add: single-number-ii solution in go (#46)

Author: cosmicray001

README.md

@@ -140,7 +140,7 @@ LeetCode
 |0134|[Gas Station](https://leetcode.com/problems/gas-station/) || [c++](./src/0134-Gas-Station/0134.cpp) |[python](./src/0134-Gas-Station/0134.py)|||||Medium|
 |0135|[Candy](https://leetcode.com/problems/gas-station/) || [c++](./src/0134-Gas-Station/0134.cpp) |[python](./src/0134-Gas-Station/0134.py)|||||Hard|
 |0136|[Single Number](https://leetcode.com/problems/single-number/) || [c++](./src/0136-Single-Number/0136.cpp) |[python](./src/0136-Single-Number/0136.py)|[go](./src/0136-Single-Number/0136.go)||||Easy|
-|0137|[Single Number II](https://leetcode.com/problems/single-number-ii/) || [c++](./src/0137-Single-Number-II/0137.cpp) |[python](./src/0137-Single-Number-II/0137.py)|||||Medium|
+|0137|[Single Number II](https://leetcode.com/problems/single-number-ii/) || [c++](./src/0137-Single-Number-II/0137.cpp) |[python](./src/0137-Single-Number-II/0137.py)|[go](./src/0137-Single-Number-II/0137.go)||||Medium|
 |0138|[Copy List with Random Pointer](https://leetcode.com/problems/copy-list-with-random-pointer/) || [c++](./src/0138-Copy-List-with-Random-Pointer/0138.cpp) |[python](./src/0138-Copy-List-with-Random-Pointer/0138.py)|||||Medium|
 |0139|[Word Break](https://leetcode.com/problems/word-break/) || [c++](./src/0139-Word-Break/0139.cpp) |[python](./src/0139-Word-Break/0139.py)|||||Medium|
 |0140|[Word Break II](https://leetcode.com/problems/word-break-ii/) || [c++](./src/0140-Word-Break-II/0140.cpp) |[python](./src/0140-Word-Break-II/0140.py)|||||Hard|

src/0137-Single-Number-II/0137.go

@@ -0,0 +1,17 @@
+package singlenumberii
+
+func singleNumber(nums []int) int {
+	ans := 0
+	for bit := 1; bit != 0; bit <<= 1 {
+		count := 0
+		for _, num := range nums {
+			if num&bit != 0 {
+				count++
+			}
+		}
+		if count%3 == 1 {
+			ans |= bit
+		}
+	}
+	return ans
+}