diff --git a/.coveragerc b/.coveragerc
deleted file mode 100644
index 2a9fb1b..0000000
--- a/.coveragerc
+++ /dev/null
@@ -1,29 +0,0 @@
-[run]
-parallel = True
-branch = True
-source = $TOP
-data_file = $TOP/.coverage
-omit =
-    .tox/*
-    /usr/*
-    */tmp*
-    setup.py
-
-[report]
-exclude_lines =
-    # Have to re-enable the standard pragma
-    \#\s*pragma: no cover
-
-    # Don't complain if tests don't hit defensive assertion code:
-    ^\s*raise AssertionError\b
-    ^\s*raise NotImplementedError\b
-    ^\s*return NotImplemented\b
-    ^\s*raise$
-
-    # Don't complain if non-runnable code isn't run:
-    ^if __name__ == ['"]__main__['"]:$
-
-[html]
-directory = coverage-html
-
-# vim:ft=dosini
diff --git a/.github/actions/pre-test/action.yml b/.github/actions/pre-test/action.yml
new file mode 100644
index 0000000..560b489
--- /dev/null
+++ b/.github/actions/pre-test/action.yml
@@ -0,0 +1,4 @@
+runs:
+  using: composite
+  steps:
+  - uses: actions/setup-go@v3
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..fabc8af
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,19 @@
+name: main
+
+on:
+  push:
+    branches: [main, test-me-*]
+    tags: '*'
+  pull_request:
+
+jobs:
+  main-windows:
+    uses: asottile/workflows/.github/workflows/tox.yml@v1.7.0
+    with:
+      env: '["py39"]'
+      os: windows-latest
+  main-linux:
+    uses: asottile/workflows/.github/workflows/tox.yml@v1.7.0
+    with:
+      env: '["pypy3", "py39", "py310", "py311", "py312", "py313"]'
+      os: ubuntu-latest
diff --git a/.gitignore b/.gitignore
index 45c9677..978f284 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,13 +1,7 @@
 *.egg-info
-*.iml
-*.py[cod]
+*.pyc
 *.so
-.*.sw[a-z]
-.coverage
-.tox
-.venv.touch
-/.cache
+/.coverage
+/.tox
 /build
-/venv*
-coverage-html
-dist
+/dist
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 26efa14..061fab0 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,22 +1,49 @@
--   repo: https://github.com/pre-commit/pre-commit-hooks.git
-    sha: v0.7.0
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
     hooks:
     -   id: trailing-whitespace
     -   id: end-of-file-fixer
-    -   id: autopep8-wrapper
-    -   id: check-docstring-first
     -   id: check-yaml
     -   id: debug-statements
+    -   id: double-quote-string-fixer
+    -   id: name-tests-test
     -   id: requirements-txt-fixer
-    -   id: flake8
--   repo: https://github.com/asottile/reorder_python_imports.git
-    sha: v0.3.1
+-   repo: https://github.com/asottile/setup-cfg-fmt
+    rev: v2.7.0
+    hooks:
+    -   id: setup-cfg-fmt
+-   repo: https://github.com/asottile/reorder-python-imports
+    rev: v3.14.0
     hooks:
     -   id: reorder-python-imports
+        args: [--py39-plus, --add-import, 'from __future__ import annotations']
+-   repo: https://github.com/asottile/add-trailing-comma
+    rev: v3.1.0
+    hooks:
+    -   id: add-trailing-comma
+-   repo: https://github.com/asottile/pyupgrade
+    rev: v3.19.1
+    hooks:
+    -   id: pyupgrade
+        args: [--py39-plus]
+-   repo: https://github.com/hhatto/autopep8
+    rev: v2.3.1
+    hooks:
+    -   id: autopep8
+-   repo: https://github.com/PyCQA/flake8
+    rev: 7.1.1
+    hooks:
+    -   id: flake8
+-   repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.14.1
+    hooks:
+    -   id: mypy
+        exclude: ^testing/
 -   repo: local
     hooks:
     -   id: gofmt
         name: gofmt
         language: system
         entry: gofmt -l -w
-        files: \.go$
+        types: [go]
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index f2e3337..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,21 +0,0 @@
-language: python
-sudo: false
-matrix:
-    include:
-        -   env: TOXENV=py27 GO=1.6
-        -   env: TOXENV=py27 GO=1.7
-        -   env: TOXENV=py35 GO=1.7
-            python: 3.5
-        -   env: TOXENV=py36 GO=1.7
-            python: 3.6
-        -   env: TOXENV=pypy GO=1.7
-            python: pypy
-install:
-    - eval "$(gimme $GO)"
-    - pip install coveralls tox
-script: tox
-after_success: coveralls
-cache:
-    directories:
-        - $HOME/.cache/pip
-        - $HOME/.pre-commit
diff --git a/Makefile b/Makefile
deleted file mode 100644
index a27d50a..0000000
--- a/Makefile
+++ /dev/null
@@ -1,23 +0,0 @@
-REBUILD_FLAG =
-
-.PHONY: all
-all: venv test
-
-.PHONY: venv
-venv: .venv.touch
-	tox -e venv $(REBUILD_FLAG)
-
-.PHONY: test
-test: .venv.touch
-	tox $(REBUILD_FLAG)
-
-.venv.touch: setup.py requirements-dev.txt
-	$(eval REBUILD_FLAG := --recreate)
-	touch .venv.touch
-
-.PHONY: clean
-clean:
-	find -name '*.pyc' -delete
-	rm -rf .tox
-	rm -rf ./venv-*
-	rm -f .venv.touch
diff --git a/README.md b/README.md
index 184c5f5..6ed218b 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,15 @@
-[![Build Status](https://travis-ci.org/asottile/setuptools-golang.svg?branch=master)](https://travis-ci.org/asottile/setuptools-golang)
-[![Coverage Status](https://img.shields.io/coveralls/asottile/setuptools-golang.svg?branch=master)](https://coveralls.io/r/asottile/setuptools-golang)
+# DEPRECATED
+
+it turns out multiple go shared objects in a single process is not supported
+
+it likely broke in [go 1.21] and there is no intention to fix it :(
+
+[go 1.21]: https://github.com/golang/go/issues/65050#issue-2074509727
+
+___
+
+[![build status](https://github.com/asottile/setuptools-golang/actions/workflows/main.yml/badge.svg)](https://github.com/asottile/setuptools-golang/actions/workflows/main.yml)
+[![pre-commit.ci status](https://results.pre-commit.ci/badge/github/asottile/setuptools-golang/main.svg)](https://results.pre-commit.ci/latest/github/asottile/setuptools-golang/main)
 
 setuptools-golang
 =================
@@ -8,10 +18,15 @@ A setuptools extension for building cpython extensions written in golang.
 
 ## Requirements
 
-This requires golang >= 1.5.  It is currently tested against 1.6 and 1.7.
+This requires golang >= 1.5.
 
-This requires python >= 2.7.  It is currently tested against 2.7, 3.5, 3.6,
-and pypy.
+This requires python >= 3.7.  It is currently tested against python3 and pypy3.
+
+## Platform Support
+
+- linux
+- macOS
+- win32
 
 ## Usage
 
@@ -19,6 +34,11 @@ Add `setuptools-golang` to the `setup_requires` in your setup.py and
 `build_golang={'root': ...}`.  `root` refers to the root go import path of
 your project.
 
+By default, `setuptools-golang` will strip all binaries. This can be disabled
+by adding `'strip': False` to `build_golang`. This will increase the size of
+the extension, but the binaries contain debugging information and symbols.
+
+
 An extension must be a single file in the `main` go package (though the entire
 `main` package will be built into the extension).  That package may import
 other code.
@@ -60,6 +80,30 @@ Double check that your import is correct.
 
 You've probably mistyped an import.  Double check that your import is correct.
 
+### `duplicate symbol _XXX in: _cgo_export.o mod.cgo2.o`
+
+For example:
+```
+# github.com/asottile/dockerfile/pylib
+duplicate symbol _PyDockerfile_GoParseError in:
+    $WORK/github.com/asottile/dockerfile/pylib/_obj/_cgo_export.o
+    $WORK/github.com/asottile/dockerfile/pylib/_obj/main.cgo2.o
+```
+
+Make sure to mark global variables defined in C as `extern`.
+[Here's an example PR](https://github.com/asottile/dockerfile/pull/8)
+
+### repeated rebuilds can be slow
+
+setuptools-golang attempts to make builds more repeatable by using a separate
+`GOPATH` -- if you'd like to reuse a GOPATH you can set the
+`SETUPTOOLS_GOLANG_GOPATH` environment variable:
+
+```console
+$ SETUPTOOLS_GOLANG_GOPATH=~/go pip install .
+...
+```
+
 ## Building manylinux wheels
 
 `setuptools-golang` also provides a tool for building
@@ -78,7 +122,6 @@ $ setuptools-golang-build-manylinux-wheels
 total 8092
 drwxrwxr-x  2 1000 1000    4096 Feb  1 04:16 .
 drwxr-xr-x 41 root root    4096 Feb  1 04:15 ..
--rw-r--r--  1 1000 1000 2065095 Feb  1 04:16 setuptools_golang_examples-0.1.1-cp27-cp27mu-manylinux1_x86_64.whl
 -rw-r--r--  1 1000 1000 2063299 Feb  1 04:16 setuptools_golang_examples-0.1.1-cp34-cp34m-manylinux1_x86_64.whl
 -rw-r--r--  1 1000 1000 2064862 Feb  1 04:16 setuptools_golang_examples-0.1.1-cp35-cp35m-manylinux1_x86_64.whl
 -rw-r--r--  1 1000 1000 2064873 Feb  1 04:16 setuptools_golang_examples-0.1.1-cp36-cp36m-manylinux1_x86_64.whl
diff --git a/requirements-dev.txt b/requirements-dev.txt
index aa5127b..b8acb1f 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,4 +1,3 @@
--e .
+covdefaults>=1.2.0
 coverage-enable-subprocess
-pre-commit
 pytest
diff --git a/setup.cfg b/setup.cfg
index e57d130..adde60a 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,2 +1,52 @@
-[wheel]
+[metadata]
+name = setuptools_golang
+version = 2.9.0
+description = A setuptools extension for building cpython extensions written in golang.
+long_description = file: README.md
+long_description_content_type = text/markdown
+url = https://github.com/asottile/setuptools-golang
+author = Anthony Sottile
+author_email = asottile@umich.edu
+license = MIT
+license_files = LICENSE
+classifiers =
+    License :: OSI Approved :: MIT License
+    Programming Language :: Python :: 3
+    Programming Language :: Python :: 3 :: Only
+    Programming Language :: Python :: Implementation :: CPython
+    Programming Language :: Python :: Implementation :: PyPy
+
+[options]
+py_modules = setuptools_golang
+install_requires =
+    setuptools
+python_requires = >=3.9
+
+[options.entry_points]
+console_scripts =
+    setuptools-golang-build-manylinux-wheels = setuptools_golang:build_manylinux_wheels
+distutils.setup_keywords =
+    build_golang = setuptools_golang:set_build_ext
+
+[bdist_wheel]
 universal = True
+
+[coverage:run]
+plugins = covdefaults
+parallel = True
+source = $PWD
+data_file = $PWD/.coverage
+
+[mypy]
+check_untyped_defs = true
+disallow_any_generics = true
+disallow_incomplete_defs = true
+disallow_untyped_defs = true
+warn_redundant_casts = true
+warn_unused_ignores = true
+
+[mypy-testing.*]
+disallow_untyped_defs = false
+
+[mypy-tests.*]
+disallow_untyped_defs = false
diff --git a/setup.py b/setup.py
index 854251e..3d93aef 100644
--- a/setup.py
+++ b/setup.py
@@ -1,35 +1,4 @@
-from setuptools import setup
-
+from __future__ import annotations
 
-setup(
-    name='setuptools-golang',
-    description=(
-        'A setuptools extension for building cpython extensions written in '
-        'golang.'
-    ),
-    url='https://github.com/asottile/setuptools-golang',
-    version='1.0.0',
-    author='Anthony Sottile',
-    author_email='asottile@umich.edu',
-    classifiers=[
-        'License :: OSI Approved :: MIT License',
-        'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.7',
-        'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.5',
-        'Programming Language :: Python :: 3.6',
-        'Programming Language :: Python :: Implementation :: CPython',
-        'Programming Language :: Python :: Implementation :: PyPy',
-    ],
-    py_modules=['setuptools_golang'],
-    install_requires=[],
-    entry_points={
-        'console_scripts': [
-            'setuptools-golang-build-manylinux-wheels = '
-            'setuptools_golang:build_manylinux_wheels',
-        ],
-        'distutils.setup_keywords': [
-            'build_golang = setuptools_golang:set_build_ext',
-        ],
-    },
-)
+from setuptools import setup
+setup()
diff --git a/setuptools_golang.py b/setuptools_golang.py
index 55dbed3..e26543d 100644
--- a/setuptools_golang.py
+++ b/setuptools_golang.py
@@ -1,62 +1,139 @@
-from __future__ import print_function
-from __future__ import unicode_literals
+from __future__ import annotations
 
+import argparse
 import contextlib
+import copy
+import errno
 import os
-import pipes
+import shlex
 import shutil
+import stat
 import subprocess
 import sys
 import tempfile
-
+from collections.abc import Generator
+from collections.abc import Sequence
+from types import TracebackType
+from typing import Any
+from typing import Callable
+
+from distutils.ccompiler import CCompiler
+from distutils.dist import Distribution
+from setuptools import Extension
 from setuptools.command.build_ext import build_ext as _build_ext
 
 
-def _get_cflags(compiler):
-    return ' '.join('-I{}'.format(p) for p in compiler.include_dirs)
-
-
-def _check_call(cmd, cwd, env):
-    envparts = [
-        '{}={}'.format(k, pipes.quote(v))
-        for k, v in sorted(tuple(env.items()))
-    ]
-    print(
-        '$ {}'.format(' '.join(envparts + [pipes.quote(p) for p in cmd])),
-        file=sys.stderr,
-    )
-    subprocess.check_call(cmd, cwd=cwd, env=dict(os.environ, **env))
+def rmtree(path: str) -> None:
+    """Newer golang uses readonly dirs & files for module cache."""
+    def handle_remove_readonly(
+            func: Callable[..., Any],
+            path: str,
+            exc: tuple[type[BaseException], BaseException, TracebackType],
+    ) -> None:
+        excvalue = exc[1]
+        if (
+                isinstance(excvalue, OSError) and
+                func in (os.rmdir, os.remove, os.unlink) and
+                excvalue.errno == errno.EACCES
+        ):
+            for p in (path, os.path.dirname(path)):
+                os.chmod(p, os.stat(p).st_mode | stat.S_IWUSR)
+            func(path)
+        else:
+            raise
+    shutil.rmtree(path, ignore_errors=False, onerror=handle_remove_readonly)
 
 
 @contextlib.contextmanager
-def _tmpdir():
+def _tmpdir() -> Generator[str]:
     tempdir = tempfile.mkdtemp()
     try:
         yield tempdir
     finally:
-        shutil.rmtree(tempdir)
-
+        rmtree(tempdir)
+
+
+def _get_cflags(
+        compiler: CCompiler,
+        macros: Sequence[tuple[str, str | None]],
+) -> str:
+    args = [f'-I{p}' for p in compiler.include_dirs]
+    for macro_name, macro_value in macros:
+        if macro_value is None:
+            args.append(f'-D{macro_name}')
+        else:
+            args.append(f'-D{macro_name}={macro_value}')
+    return ' '.join(args)
+
+
+LFLAG_CLANG = '-Wl,-undefined,dynamic_lookup'
+LFLAG_GCC = '-Wl,--unresolved-symbols=ignore-all'
+LFLAGS = (LFLAG_CLANG, LFLAG_GCC)
+
+
+def _get_ldflags() -> str:
+    """Determine the correct link flags.  This attempts compiles similar
+    to how autotools does feature detection.
+    """
+    # windows gcc does not support linking with unresolved symbols
+    if sys.platform == 'win32':  # pragma: win32 cover
+        libs = os.path.join(sys.base_prefix, 'libs')
+        return f'-L{libs} -lpython{sys.version_info[0]}'
+    else:  # pragma: win32 no cover
+        cc = subprocess.check_output(('go', 'env', 'CC')).decode().strip()
+
+        with _tmpdir() as tmpdir:
+            testf = os.path.join(tmpdir, 'test.c')
+            with open(testf, 'w') as f:
+                f.write('int f(int); int main(void) { return f(0); }\n')
+
+            for lflag in LFLAGS:  # pragma: no cover (platform specific)
+                try:
+                    subprocess.check_call((cc, testf, lflag), cwd=tmpdir)
+                    return lflag
+                except subprocess.CalledProcessError:
+                    pass
+            else:  # pragma: no cover (platform specific)
+                # wellp, none of them worked, fall back to gcc and they'll get
+                # a hopefully reasonable error message
+                return LFLAG_GCC
+
+
+def _check_call(cmd: tuple[str, ...], cwd: str, env: dict[str, str]) -> None:
+    envparts = [f'{k}={shlex.quote(v)}' for k, v in sorted(tuple(env.items()))]
+    print(f'$ {" ".join(envparts)} {shlex.join(cmd)}', file=sys.stderr)
+    subprocess.check_call(cmd, cwd=cwd, env=dict(os.environ, **env))
 
-def _get_build_extension_method(base, root):
-    def build_extension(self, ext):
-        def _raise_error(msg):
-            raise IOError(
-                'Error building extension `{}`: '.format(ext.name) + msg,
-            )
 
+def _get_build_extension_method(
+        base: type[_build_ext],
+        root: str,
+        strip: bool,
+) -> Callable[[_build_ext, Extension], None]:
+    def build_extension(self: _build_ext, ext: Extension) -> None:
         # If there are no .go files then the parent should handle this
         if not any(source.endswith('.go') for source in ext.sources):
-            return base.build_extension(self, ext)
+            # the base class may mutate `self.compiler`
+            compiler = copy.deepcopy(self.compiler)
+            self.compiler, compiler = compiler, self.compiler
+            try:
+                return base.build_extension(self, ext)
+            finally:
+                self.compiler, compiler = compiler, self.compiler
 
         if len(ext.sources) != 1:
-            _raise_error(
-                'sources must be a single file in the `main` package.\n'
-                'Recieved: {!r}'.format(ext.sources)
+            raise OSError(
+                f'Error building extension `{ext.name}`: '
+                f'sources must be a single file in the `main` package.\n'
+                f'Received: {ext.sources!r}',
             )
 
         main_file, = ext.sources
         if not os.path.exists(main_file):
-            _raise_error('{} does not exist'.format(main_file))
+            raise OSError(
+                f'Error building extension `{ext.name}`: '
+                f'{main_file} does not exist',
+            )
         main_dir = os.path.dirname(main_file)
 
         # Copy the package into a temporary GOPATH environment
@@ -64,75 +141,100 @@ def _raise_error(msg):
             root_path = os.path.join(tempdir, 'src', root)
             # Make everything but the last directory (copytree interface)
             os.makedirs(os.path.dirname(root_path))
-            shutil.copytree('.', root_path)
+            shutil.copytree('.', root_path, symlinks=True)
             pkg_path = os.path.join(root_path, main_dir)
 
-            env = {'GOPATH': tempdir}
+            gopath = os.environ.get('SETUPTOOLS_GOLANG_GOPATH', tempdir)
+            env = {'GOPATH': gopath}
             cmd_get = ('go', 'get', '-d')
             _check_call(cmd_get, cwd=pkg_path, env=env)
 
             env.update({
-                'CGO_CFLAGS': _get_cflags(self.compiler),
-                'CGO_LDFLAGS': '-Wl,--unresolved-symbols=ignore-all',
+                'CGO_CFLAGS': _get_cflags(
+                    self.compiler, ext.define_macros or (),
+                ),
+                'CGO_LDFLAGS': _get_ldflags(),
             })
-            cmd_build = (
+
+            cmd_build: tuple[str, ...] = (
                 'go', 'build', '-buildmode=c-shared',
                 '-o', os.path.abspath(self.get_ext_fullpath(ext.name)),
             )
+            # "-s" omits the symbol table and debug information
+            # "-w" omits DWARF debugging information
+            if strip:
+                cmd_build = (*cmd_build, '-ldflags=-s -w')
+
             _check_call(cmd_build, cwd=pkg_path, env=env)
 
     return build_extension
 
 
-def _get_build_ext_cls(base, root):
-    class build_ext(base):
-        build_extension = _get_build_extension_method(base, root)
-
-    return build_ext
+def _get_build_ext_cls(
+        base: type[_build_ext],
+        root: str,
+        strip: bool = True,
+) -> type[_build_ext]:
+    attrs = {'build_extension': _get_build_extension_method(base, root, strip)}
+    return type('build_ext', (base,), attrs)
 
 
-def set_build_ext(dist, attr, value):
-    root = value['root']
+def set_build_ext(
+        dist: Distribution,
+        attr: str,
+        value: dict[str, Any],
+) -> None:
     base = dist.cmdclass.get('build_ext', _build_ext)
-    dist.cmdclass['build_ext'] = _get_build_ext_cls(base, root)
-
-
-GOLANG = 'https://storage.googleapis.com/golang/go1.7.5.linux-amd64.tar.gz'
-WHEEL_ARGS = '--no-deps --wheel-dir /tmp /dist/*.tar.gz'
+    dist.cmdclass['build_ext'] = _get_build_ext_cls(base, **value)
+
+
+GOLANG = 'https://storage.googleapis.com/golang/go{}.linux-amd64.tar.gz'
+SCRIPT = '''\
+cd /tmp
+curl {golang} --silent --location | tar -xz
+export PATH="/tmp/go/bin:$PATH" HOME=/tmp
+for py in {pythons}; do
+    "/opt/python/$py/bin/pip" wheel --no-deps --wheel-dir /tmp /dist/*.tar.gz
+done
+ls *.whl | xargs -n1 --verbose auditwheel repair --wheel-dir /dist
+ls -al /dist
+'''
+
+
+def build_manylinux_wheels(
+        argv: Sequence[str] | None = None,
+) -> int:  # pragma: no cover
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        '--golang', default='1.17.1',
+        help='Override golang version (default %(default)s)',
+    )
+    parser.add_argument(
+        '--pythons', default='cp37-cp37m',
+        help='Override pythons to build (default %(default)s)',
+    )
+    args = parser.parse_args(argv)
 
+    golang = GOLANG.format(args.golang)
+    pythons = ' '.join(args.pythons.split(','))
 
-def build_manylinux_wheels(argv=None):  # pragma: no cover
     assert os.path.exists('setup.py')
-    shutil.rmtree('dist')
+    if os.path.exists('dist'):
+        shutil.rmtree('dist')
     os.makedirs('dist')
     _check_call(('python', 'setup.py', 'sdist'), cwd='.', env={})
     _check_call(
         (
-            'docker', 'run',
-            '--volume', '{}:/dist:rw'.format(os.path.abspath('dist')),
-            # I'd use --user, but this breaks git:
-            # http://stackoverflow.com/a/20272540/812183
-            '--env', 'UID={}'.format(os.getuid()),
-            '--env', 'GID={}'.format(os.getgid()),
+            'docker', 'run', '--rm',
+            '--volume', f'{os.path.abspath("dist")}:/dist:rw',
+            '--user', f'{os.getuid()}:{os.getgid()}',
             'quay.io/pypa/manylinux1_x86_64:latest',
-            'bash', '-exc',
-            'cd /tmp\n'
-            'wget {golang} -q --no-check-certificate -O /tmp/golang.tar.gz\n'
-            'tar -xf /tmp/golang.tar.gz\n'
-            'export GOROOT=/tmp/go\n'
-            'export PATH="$GOROOT/bin:$PATH"\n'
-            '/opt/python/cp27-cp27mu/bin/pip wheel {wheel_args}\n'
-            '/opt/python/cp34-cp34m/bin/pip wheel {wheel_args}\n'
-            '/opt/python/cp35-cp35m/bin/pip wheel {wheel_args}\n'
-            '/opt/python/cp36-cp36m/bin/pip wheel {wheel_args}\n'
-            'mkdir /tmp/whls\n'
-            'ls *.whl | xargs -n1 --verbose auditwheel repair -w /tmp/whls\n'
-            'cp /tmp/whls/* /dist\n'
-            'chown "$UID:$GID" /dist/*\n'
-            'ls /dist -al\n'.format(golang=GOLANG, wheel_args=WHEEL_ARGS),
+            'bash', '-o', 'pipefail', '-euxc',
+            SCRIPT.format(golang=golang, pythons=pythons),
         ),
         cwd='.', env={},
     )
     print('*' * 79)
     print('Your wheels have been built into ./dist')
     print('*' * 79)
+    return 0
diff --git a/testing/dangling_symlink/dangling b/testing/dangling_symlink/dangling
new file mode 120000
index 0000000..ee1f6cb
--- /dev/null
+++ b/testing/dangling_symlink/dangling
@@ -0,0 +1 @@
+does_not_exist
\ No newline at end of file
diff --git a/testing/dangling_symlink/fake.go b/testing/dangling_symlink/fake.go
new file mode 100644
index 0000000..38dd16d
--- /dev/null
+++ b/testing/dangling_symlink/fake.go
@@ -0,0 +1,3 @@
+package main
+
+func main() {}
diff --git a/testing/dangling_symlink/go.mod b/testing/dangling_symlink/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/dangling_symlink/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/dangling_symlink/setup.py b/testing/dangling_symlink/setup.py
new file mode 100644
index 0000000..1c6c660
--- /dev/null
+++ b/testing/dangling_symlink/setup.py
@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+from setuptools import Extension
+from setuptools import setup
+
+
+setup(
+    name='fake',
+    ext_modules=[Extension('fake', ['fake.go'])],
+    build_golang={'root': 'github.com/asottile/fake'},
+    # Would do this, but we're testing *our* implementation and this would
+    # install from pypi.  We can rely on setuptools-golang being already
+    # installed under test.
+    # setup_requires=['setuptools-golang'],
+)
diff --git a/testing/defines/go.mod b/testing/defines/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/defines/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/defines/setup.py b/testing/defines/setup.py
new file mode 100644
index 0000000..ae5f84b
--- /dev/null
+++ b/testing/defines/setup.py
@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from setuptools import Extension
+from setuptools import setup
+
+
+setup(
+    name='sum',
+    ext_modules=[
+        Extension(
+            'sum', ['sum.go'],
+            define_macros=[('SUM_A', None), ('SUM_B', '2')],
+        ),
+    ],
+    build_golang={'root': 'github.com/asottile/fake'},
+    # Would do this, but we're testing *our* implementation and this would
+    # install from pypi.  We can rely on setuptools-golang being already
+    # installed under test.
+    # setup_requires=['setuptools-golang'],
+)
diff --git a/testing/defines/sum.c b/testing/defines/sum.c
new file mode 100644
index 0000000..ec311ec
--- /dev/null
+++ b/testing/defines/sum.c
@@ -0,0 +1,29 @@
+#include <Python.h>
+
+/* Will come from go */
+PyObject* sum(PyObject* , PyObject*);
+
+/* To shim go's missing variadic function support */
+int PyArg_ParseTuple_ll(PyObject* args, long* a, long* b) {
+    return PyArg_ParseTuple(args, "ll", a, b);
+}
+
+/* demo that macro_defines works */
+#if defined(SUM_A) && SUM_B >= 2
+static struct PyMethodDef methods[] = {
+    {"sum", (PyCFunction)sum, METH_VARARGS},
+    {NULL, NULL}
+};
+#endif
+
+static struct PyModuleDef module = {
+    PyModuleDef_HEAD_INIT,
+    "sum",
+    NULL,
+    -1,
+    methods
+};
+
+PyMODINIT_FUNC PyInit_sum(void) {
+    return PyModule_Create(&module);
+}
diff --git a/testing/defines/sum.go b/testing/defines/sum.go
new file mode 100644
index 0000000..9fdd006
--- /dev/null
+++ b/testing/defines/sum.go
@@ -0,0 +1,17 @@
+package main
+
+// #include <Python.h>
+// int PyArg_ParseTuple_ll(PyObject*, long*, long*);
+import "C"
+
+//export sum
+func sum(self *C.PyObject, args *C.PyObject) *C.PyObject {
+	var a C.long
+	var b C.long
+	if C.PyArg_ParseTuple_ll(args, &a, &b) == 0 {
+		return nil
+	}
+	return C.PyLong_FromLong(a + b)
+}
+
+func main() {}
diff --git a/testing/gomodules/go.mod b/testing/gomodules/go.mod
new file mode 100644
index 0000000..a622a41
--- /dev/null
+++ b/testing/gomodules/go.mod
@@ -0,0 +1,5 @@
+module github.com/asottile/setuptools-golang/testing/gomodules
+
+go 1.14
+
+require github.com/golang/example v0.0.0-20170904185048-46695d81d1fa
diff --git a/testing/gomodules/go.sum b/testing/gomodules/go.sum
new file mode 100644
index 0000000..6cb484e
--- /dev/null
+++ b/testing/gomodules/go.sum
@@ -0,0 +1,2 @@
+github.com/golang/example v0.0.0-20170904185048-46695d81d1fa h1:iqCQC2Z53KkwGgTN9szyL4q0OQHmuNjeoNnMT6lk66k=
+github.com/golang/example v0.0.0-20170904185048-46695d81d1fa/go.mod h1:tO/5UvQ/uKigUjQBPqzstj6uxd3fUIjddi19DxGJeWg=
diff --git a/testing/gomodules/reversemsg.go b/testing/gomodules/reversemsg.go
new file mode 100644
index 0000000..8e39a39
--- /dev/null
+++ b/testing/gomodules/reversemsg.go
@@ -0,0 +1,19 @@
+package main
+
+// #include <Python.h>
+import "C"
+
+import (
+	"fmt"
+
+	"github.com/golang/example/stringutil"
+)
+
+//export reversemsg
+func reversemsg() *C.PyObject {
+	fmt.Print(stringutil.Reverse("elpmaxe tset"))
+
+	return C.Py_None
+}
+
+func main() {}
diff --git a/testing/gomodules/reversemsg_support.go b/testing/gomodules/reversemsg_support.go
new file mode 100644
index 0000000..b901d17
--- /dev/null
+++ b/testing/gomodules/reversemsg_support.go
@@ -0,0 +1,23 @@
+package main
+
+// #include <Python.h>
+//
+// PyObject* reversemsg();
+//
+// static struct PyMethodDef methods[] = {
+//     {"reversemsg", (PyCFunction)reversemsg, METH_NOARGS},
+//     {NULL, NULL}
+// };
+//
+// static struct PyModuleDef module = {
+//     PyModuleDef_HEAD_INIT,
+//     "gomodules",
+//     NULL,
+//     -1,
+//     methods
+// };
+//
+// PyMODINIT_FUNC PyInit_gomodules(void) {
+//     return PyModule_Create(&module);
+// }
+import "C"
diff --git a/testing/gomodules/setup.py b/testing/gomodules/setup.py
new file mode 100644
index 0000000..66fed65
--- /dev/null
+++ b/testing/gomodules/setup.py
@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+from setuptools import Extension
+from setuptools import setup
+
+
+setup(
+    name='gomod',
+    ext_modules=[Extension('gomodules', ['reversemsg.go'])],
+    build_golang={
+        'root': 'github.com/asottile/setuptools-golang/testing/gomodules',
+    },
+    # Would do this, but we're testing *our* implementation and this would
+    # install from pypi.  We can rely on setuptools-golang being already
+    # installed under test.
+    # setup_requires=['setuptools-golang'],
+)
diff --git a/testing/imports_gh/go.mod b/testing/imports_gh/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/imports_gh/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/imports_gh/red.c b/testing/imports_gh/red.c
index 7660ed9..59fa186 100644
--- a/testing/imports_gh/red.c
+++ b/testing/imports_gh/red.c
@@ -1,11 +1,5 @@
 #include <Python.h>
 
-#if PY_MAJOR_VERSION >= 3
-#define PyRed_Bytes_AS_STRING PyBytes_AS_STRING
-#else
-#define PyRed_Bytes_AS_STRING PyString_AS_STRING
-#endif
-
 /* Will come from go */
 PyObject* red(PyObject*);
 
@@ -20,7 +14,7 @@ void PyRed_DECREF(PyObject* obj) {
 }
 
 const char* PyRed_Bytes_AsString(PyObject* s) {
-    return PyRed_Bytes_AS_STRING(s);
+    return PyBytes_AS_STRING(s);
 }
 
 static struct PyMethodDef methods[] = {
@@ -28,7 +22,6 @@ static struct PyMethodDef methods[] = {
     {NULL, NULL}
 };
 
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef module = {
     PyModuleDef_HEAD_INIT,
     "red",
@@ -40,8 +33,3 @@ static struct PyModuleDef module = {
 PyMODINIT_FUNC PyInit_red(void) {
     return PyModule_Create(&module);
 }
-#else
-PyMODINIT_FUNC initred(void) {
-    Py_InitModule3("red", methods, NULL);
-}
-#endif
diff --git a/testing/imports_gh/setup.py b/testing/imports_gh/setup.py
index 6e98f79..b9fcc1e 100644
--- a/testing/imports_gh/setup.py
+++ b/testing/imports_gh/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import setup
 
diff --git a/testing/internal_imports/go.mod b/testing/internal_imports/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/internal_imports/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/internal_imports/hello_lib/hello_lib.c b/testing/internal_imports/hello_lib/hello_lib.c
index 45c9e4f..d65e23c 100644
--- a/testing/internal_imports/hello_lib/hello_lib.c
+++ b/testing/internal_imports/hello_lib/hello_lib.c
@@ -1,11 +1,5 @@
 #include <Python.h>
 
-#if PY_MAJOR_VERSION >= 3
-#define PyHelloLib_Bytes_AS_STRING PyBytes_AS_STRING
-#else
-#define PyHelloLib_Bytes_AS_STRING PyString_AS_STRING
-#endif
-
 /* Will come from go */
 PyObject* ohai(PyObject*);
 
@@ -20,7 +14,7 @@ void PyHelloLib_DECREF(PyObject* obj) {
 }
 
 const char* PyHelloLib_Bytes_AsString(PyObject* s) {
-    return PyHelloLib_Bytes_AS_STRING(s);
+    return PyBytes_AS_STRING(s);
 }
 
 static struct PyMethodDef methods[] = {
@@ -28,7 +22,6 @@ static struct PyMethodDef methods[] = {
     {NULL, NULL}
 };
 
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef module = {
     PyModuleDef_HEAD_INIT,
     "hello_lib",
@@ -40,8 +33,3 @@ static struct PyModuleDef module = {
 PyMODINIT_FUNC PyInit_hello_lib(void) {
     return PyModule_Create(&module);
 }
-#else
-PyMODINIT_FUNC inithello_lib(void) {
-    Py_InitModule3("hello_lib", methods, NULL);
-}
-#endif
diff --git a/testing/internal_imports/setup.py b/testing/internal_imports/setup.py
index 8fd2741..f3d284e 100644
--- a/testing/internal_imports/setup.py
+++ b/testing/internal_imports/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import setup
 
diff --git a/testing/multidir/dir2/sum_support.go b/testing/multidir/dir2/sum_support.go
index 085d174..4be980c 100644
--- a/testing/multidir/dir2/sum_support.go
+++ b/testing/multidir/dir2/sum_support.go
@@ -13,7 +13,6 @@ package main
 //     {NULL, NULL}
 // };
 //
-// #if PY_MAJOR_VERSION >= 3
 // static struct PyModuleDef module = {
 //     PyModuleDef_HEAD_INIT,
 //     "sum_pure_go",
@@ -25,9 +24,4 @@ package main
 // PyMODINIT_FUNC PyInit_sum_pure_go(void) {
 //     return PyModule_Create(&module);
 // }
-// #else
-// PyMODINIT_FUNC initsum_pure_go(void) {
-//     Py_InitModule3("sum_pure_go", methods, NULL);
-// }
-// #endif
 import "C"
diff --git a/testing/multidir/go.mod b/testing/multidir/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/multidir/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/multidir/setup.py b/testing/multidir/setup.py
index 1b77eca..f2af1a9 100644
--- a/testing/multidir/setup.py
+++ b/testing/multidir/setup.py
@@ -1,12 +1,16 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import setup
 
 
 setup(
     name='multidir',
-    ext_modules=[Extension(
-        'multidir', ['dir1/sum.go', 'dir2/sum_support.go'],
-    )],
+    ext_modules=[
+        Extension(
+            'multidir', ['dir1/sum.go', 'dir2/sum_support.go'],
+        ),
+    ],
     build_golang={'root': 'github.com/asottile/fake'},
     # Would do this, but we're testing *our* implementation and this would
     # install from pypi.  We can rely on setuptools-golang being already
diff --git a/testing/notfound/go.mod b/testing/notfound/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/notfound/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/notfound/setup.py b/testing/notfound/setup.py
index 2e47064..3cab498 100644
--- a/testing/notfound/setup.py
+++ b/testing/notfound/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import setup
 
diff --git a/testing/project_with_c/go.mod b/testing/project_with_c/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/project_with_c/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/project_with_c/project_with_c.c b/testing/project_with_c/project_with_c.c
index 29d4d30..e45480c 100644
--- a/testing/project_with_c/project_with_c.c
+++ b/testing/project_with_c/project_with_c.c
@@ -9,7 +9,6 @@ static struct PyMethodDef methods[] = {
     {NULL, NULL}
 };
 
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef module = {
     PyModuleDef_HEAD_INIT,
     "project_with_c",
@@ -21,8 +20,3 @@ static struct PyModuleDef module = {
 PyMODINIT_FUNC PyInit_project_with_c(void) {
     return PyModule_Create(&module);
 }
-#else
-PyMODINIT_FUNC initproject_with_c(void) {
-    Py_InitModule3("project_with_c", methods, NULL);
-}
-#endif
diff --git a/testing/project_with_c/project_with_c_sum/sum.c b/testing/project_with_c/project_with_c_sum/sum.c
index f7158c5..3d2a63c 100644
--- a/testing/project_with_c/project_with_c_sum/sum.c
+++ b/testing/project_with_c/project_with_c_sum/sum.c
@@ -13,7 +13,6 @@ static struct PyMethodDef methods[] = {
     {NULL, NULL}
 };
 
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef module = {
     PyModuleDef_HEAD_INIT,
     "project_with_c_sum.sum",
@@ -25,8 +24,3 @@ static struct PyModuleDef module = {
 PyMODINIT_FUNC PyInit_sum(void) {
     return PyModule_Create(&module);
 }
-#else
-PyMODINIT_FUNC initsum(void) {
-    Py_InitModule3("project_with_c_sum.sum", methods, NULL);
-}
-#endif
diff --git a/testing/project_with_c/setup.py b/testing/project_with_c/setup.py
index 8edff81..a604c61 100644
--- a/testing/project_with_c/setup.py
+++ b/testing/project_with_c/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import find_packages
 from setuptools import setup
diff --git a/testing/sum/go.mod b/testing/sum/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/sum/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/sum/setup.py b/testing/sum/setup.py
index 33629ca..e0fa2f1 100644
--- a/testing/sum/setup.py
+++ b/testing/sum/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import setup
 
diff --git a/testing/sum/sum.c b/testing/sum/sum.c
index 6df94ba..56cce5e 100644
--- a/testing/sum/sum.c
+++ b/testing/sum/sum.c
@@ -13,7 +13,6 @@ static struct PyMethodDef methods[] = {
     {NULL, NULL}
 };
 
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef module = {
     PyModuleDef_HEAD_INIT,
     "sum",
@@ -25,8 +24,3 @@ static struct PyModuleDef module = {
 PyMODINIT_FUNC PyInit_sum(void) {
     return PyModule_Create(&module);
 }
-#else
-PyMODINIT_FUNC initsum(void) {
-    Py_InitModule3("sum", methods, NULL);
-}
-#endif
diff --git a/testing/sum_pure_go/go.mod b/testing/sum_pure_go/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/sum_pure_go/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/sum_pure_go/setup.py b/testing/sum_pure_go/setup.py
index 776b227..4f261f9 100644
--- a/testing/sum_pure_go/setup.py
+++ b/testing/sum_pure_go/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import setup
 
diff --git a/testing/sum_pure_go/sum_support.go b/testing/sum_pure_go/sum_support.go
index 085d174..4be980c 100644
--- a/testing/sum_pure_go/sum_support.go
+++ b/testing/sum_pure_go/sum_support.go
@@ -13,7 +13,6 @@ package main
 //     {NULL, NULL}
 // };
 //
-// #if PY_MAJOR_VERSION >= 3
 // static struct PyModuleDef module = {
 //     PyModuleDef_HEAD_INIT,
 //     "sum_pure_go",
@@ -25,9 +24,4 @@ package main
 // PyMODINIT_FUNC PyInit_sum_pure_go(void) {
 //     return PyModule_Create(&module);
 // }
-// #else
-// PyMODINIT_FUNC initsum_pure_go(void) {
-//     Py_InitModule3("sum_pure_go", methods, NULL);
-// }
-// #endif
 import "C"
diff --git a/testing/sum_sub_package/go.mod b/testing/sum_sub_package/go.mod
new file mode 100644
index 0000000..f647b9d
--- /dev/null
+++ b/testing/sum_sub_package/go.mod
@@ -0,0 +1,3 @@
+module github.com/asottile/fake
+
+go 1.16
diff --git a/testing/sum_sub_package/setup.py b/testing/sum_sub_package/setup.py
index 42c77a2..6114e80 100644
--- a/testing/sum_sub_package/setup.py
+++ b/testing/sum_sub_package/setup.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from setuptools import Extension
 from setuptools import find_packages
 from setuptools import setup
@@ -7,7 +9,7 @@
     name='sum_sub_package',
     ext_modules=[Extension('sum_sub_package.sum', ['sum_sub_package/sum.go'])],
     packages=find_packages(),
-    build_golang={'root': 'github.com/asottile/fake'},
+    build_golang={'root': 'github.com/asottile/fake', 'strip': False},
     # Would do this, but we're testing *our* implementation and this would
     # install from pypi.  We can rely on setuptools-golang being already
     # installed under test.
diff --git a/testing/sum_sub_package/sum_sub_package/sum.c b/testing/sum_sub_package/sum_sub_package/sum.c
index c1e4ca6..e47af2b 100644
--- a/testing/sum_sub_package/sum_sub_package/sum.c
+++ b/testing/sum_sub_package/sum_sub_package/sum.c
@@ -13,7 +13,6 @@ static struct PyMethodDef methods[] = {
     {NULL, NULL}
 };
 
-#if PY_MAJOR_VERSION >= 3
 static struct PyModuleDef module = {
     PyModuleDef_HEAD_INIT,
     "sum_sub_package.sum",
@@ -25,8 +24,3 @@ static struct PyModuleDef module = {
 PyMODINIT_FUNC PyInit_sum(void) {
     return PyModule_Create(&module);
 }
-#else
-PyMODINIT_FUNC initsum(void) {
-    Py_InitModule3("sum_sub_package.sum", methods, NULL);
-}
-#endif
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/setuptools_golang_test.py b/tests/setuptools_golang_test.py
similarity index 54%
rename from setuptools_golang_test.py
rename to tests/setuptools_golang_test.py
index 5e8dbe2..81fdaaa 100644
--- a/setuptools_golang_test.py
+++ b/tests/setuptools_golang_test.py
@@ -1,7 +1,8 @@
-from __future__ import unicode_literals
+from __future__ import annotations
 
 import collections
 import os
+import shlex
 import subprocess
 import sys
 
@@ -13,9 +14,8 @@
 
 @pytest.fixture(autouse=True, scope='session')
 def enable_coverage_subprocesses():
-    here = os.path.dirname(os.path.abspath(__file__))
-    os.environ['TOP'] = here
-    os.environ['COVERAGE_PROCESS_START'] = os.path.join(here, '.coveragerc')
+    here = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+    os.environ['COVERAGE_PROCESS_START'] = os.path.join(here, 'setup.cfg')
 
 
 def auto_namedtuple(**kwargs):
@@ -26,14 +26,13 @@ def run(*cmd, **kwargs):
     returncode = kwargs.pop('returncode', 0)
     proc = subprocess.Popen(cmd, **kwargs)
     out, err = proc.communicate()
-    out = out.decode('UTF-8') if out is not None else None
-    err = err.decode('UTF-8') if err is not None else None
+    out = out.decode('UTF-8').replace('\r', '') if out is not None else None
+    err = err.decode('UTF-8').replace('\r', '') if err is not None else None
     if returncode is not None:
         if proc.returncode != returncode:
             raise AssertionError(
-                '{!r} returned {} (expected {})\nout:\n{}\nerr:\n{}\n'.format(
-                    cmd, proc.returncode, returncode, out, err,
-                )
+                f'{cmd!r} returned {proc.returncode} (expected {returncode})\n'
+                f'out:\n{out}\nerr:\n{err}\n',
             )
     return auto_namedtuple(returncode=proc.returncode, out=out, err=err)
 
@@ -51,18 +50,21 @@ def test_sets_cmdclass():
     assert dist.cmdclass['build_ext']
 
 
-@pytest.yield_fixture(scope='session')
+@pytest.fixture(scope='session')
 def venv(tmpdir_factory):
     """A shared virtualenv fixture, be careful not to install two of the same
     package into this -- or sadness...
     """
+    bin = 'Scripts' if sys.platform == 'win32' else 'bin'
     venv = tmpdir_factory.mktemp('venv').join('venv')
-    pip = venv.join('bin/pip').strpath
-    python = venv.join('bin/python').strpath
+    pip = venv.join(bin, 'pip').strpath
+    python = venv.join(bin, 'python').strpath
     # Make sure this virtualenv has the same executable
     run('virtualenv', venv.strpath, '-p', sys.executable)
     # Install this so we can get coverage
-    run(pip, 'install', 'coverage-enable-subprocess')
+    run(pip, 'install', 'covdefaults>=1.2.0', 'coverage-enable-subprocess')
+    # Install wheel as well so we can non-pep517
+    run(pip, 'install', 'wheel')
     # Install us!
     run(pip, 'install', '-e', '.')
     yield auto_namedtuple(venv=venv, pip=pip, python=python)
@@ -74,9 +76,9 @@ def venv(tmpdir_factory):
 @pytest.mark.parametrize(
     ('pkg', 'mod'),
     (
-        ('testing/sum', 'sum'),
-        ('testing/sum_pure_go', 'sum_pure_go'),
-        ('testing/sum_sub_package', 'sum_sub_package.sum'),
+        (os.path.join('testing', 'sum'), 'sum'),
+        (os.path.join('testing', 'sum_pure_go'), 'sum_pure_go'),
+        (os.path.join('testing', 'sum_sub_package'), 'sum_sub_package.sum'),
     ),
 )
 def test_sum_integration(venv, pkg, mod):
@@ -90,7 +92,8 @@ def test_sum_integration(venv, pkg, mod):
 
 def test_integration_project_with_c(venv):
     test_sum_integration(
-        venv, 'testing/project_with_c', 'project_with_c_sum.sum',
+        venv,
+        os.path.join('testing', 'project_with_c'), 'project_with_c_sum.sum',
     )
     out = run_output(venv.python, '-c', HELLO_WORLD)
     assert out == 'hello world\n'
@@ -100,14 +103,23 @@ def test_integration_project_with_c(venv):
 
 
 def test_integration_imports_gh(venv):
-    run(venv.pip, 'install', 'testing/imports_gh')
+    run(venv.pip, 'install', os.path.join('testing', 'imports_gh'))
     out = run_output(venv.python, '-c', RED)
-    assert out == '\x1b[31mohai\x1b[0m\n'
+    assert out == '\x1b[0;31mohai\x1b[0m\n'
+
+
+GOMOD = 'import gomodules; gomodules.reversemsg()'
+
+
+def test_integration_gomodules(venv):
+    run(venv.pip, 'install', os.path.join('testing', 'gomodules'))
+    out = run_output(venv.python, '-c', GOMOD)
+    assert out == 'test example'
 
 
 def test_integration_notfound(venv):
     ret = run(
-        venv.pip, 'install', 'testing/notfound',
+        venv.pip, 'install', os.path.join('testing', 'notfound'),
         returncode=None, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
     )
     assert ret.returncode != 0
@@ -119,7 +131,7 @@ def test_integration_notfound(venv):
 
 def test_integration_multidir(venv):
     ret = run(
-        venv.pip, 'install', 'testing/multidir',
+        venv.pip, 'install', os.path.join('testing', 'multidir'),
         returncode=None, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
     )
     assert ret.returncode != 0
@@ -133,6 +145,32 @@ def test_integration_multidir(venv):
 
 
 def test_integration_internal_imports(venv):
-    run(venv.pip, 'install', 'testing/internal_imports')
+    run(venv.pip, 'install', os.path.join('testing', 'internal_imports'))
     out = run_output(venv.python, '-c', OHAI)
     assert out == 'ohai, Anthony\n'
+
+
+def test_integration_user_gopath(venv, tmpdir):
+    testdir = os.path.join('testing', 'gomodules')
+
+    gopath = str(tmpdir.join('gopath'))
+    env = {**os.environ, 'SETUPTOOLS_GOLANG_GOPATH': gopath}
+    ret = run(
+        venv.pip, 'install', '-v', testdir,
+        env=env,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+    )
+
+    assert f'$ GOPATH={shlex.quote(gopath)} go get -d' in ret.out
+
+
+def test_integration_defines(venv):
+    run(venv.pip, 'install', os.path.join('testing', 'defines'))
+    out = run_output(venv.python, '-c', SUM.format('sum'))
+    assert out == '3\n'
+
+
+def test_regression_dangling_symlink(venv):
+    # this raises an error because of a dangling symlink
+    run(venv.pip, 'install', os.path.join('testing', 'dangling_symlink'))
diff --git a/tox.ini b/tox.ini
index 1d3428e..4e4a4dc 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,23 +1,20 @@
 [tox]
-project = setuptools-golang
-# These should match the travis env list
-envlist = py27,py35,py36,pypy
+envlist = py,pre-commit
 
 [testenv]
 deps = -rrequirements-dev.txt
-passenv = HOME GOROOT
-setenv = TOP={toxinidir}
+passenv = *
+setenv = PWD={toxinidir}
 commands =
     coverage erase
-    coverage run -m pytest {posargs:setuptools_golang_test.py}
+    coverage run -m pytest {posargs:tests}
     coverage combine
-    coverage report --show-missing --fail-under 100
-    pre-commit install -f --install-hooks
-    pre-commit run --all-files
+    coverage report
 
-[testenv:venv]
-envdir = venv-{[tox]project}
-commands =
+[testenv:pre-commit]
+skip_install = true
+deps = pre-commit
+commands = pre-commit run --all-files --show-diff-on-failure
 
 [pep8]
-ignore = E265,E309,E501
+ignore = E265,E501,W504