Disconnection from postgres-compatible google cloud AlloyDB instance hangs

• asyncpg version: 0.26.0
• PostgreSQL version: Google AlloyDB, postgres 14.4 compatible
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: I cannot reproduce the issue on a local postgres, no.
• Python version: 3.10
• Platform: Macos
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?: NA
• Can the issue be reproduced under both asyncio and
  uvloop?: I have not tried to reproduce under uvloop

I am connecting to an AlloyDB instance on Google Cloud (currently, these are available for free testing). I can connect and queries run as expected. However, connection.disconnect() hangs. I cannot reproduce this behavior locally; disconnection happens as expected. Synchronous database work with psycopg2, for example, works as expected.

This code reproduces the behavior I am seeing (running through the alloydb-auth-proxy as is required):

import asyncpg
conn = await asyncpg.connect(ALLOYDB_URI)
conn.disconnect() # hangs

I'll put in a ticket with Google as well if nothing obvious turns up here.

Start at the connection.disconnect() call in the provided AlloyDB-auth-proxy reproduction and run it against the reported Google Cloud AlloyDB setup. Compare the behavior with a local PostgreSQL installation and the existing psycopg2 behavior; done means identifying the cause of the hang and ensuring asyncpg disconnects cleanly for this setup.