Assertion failure after restarting database.

[ileitch]

Reproduction:

1. Start postgres (I'm using docker for this)
2. Run serve and make a request to an endpoint that performs a query
3. Stop postgres
4. Perform the request again, and observe the logged error:
   [ ERROR ] connection reset (error set): Connection refused (errno: 61)
5. Start postgres again
6. Perform the request again, this time the process exists with: Assertion failed: PostgresConnection deinitialized before being closed.: file /Users/ian/code/streambuddy/.build/checkouts/postgres-nio/Sources/PostgresNIO/Connection/PostgresConnection.swift, line 42

Expected outcome:
serve gracefully handles the restart and makes a new connection to postgres.

Actual outcome:
serve exits.