[slawwan]

Follow-up to #8: as suggested there, the background closure is dropped now that MagicStack/asyncpg#1361 is released in asyncpg 0.32.0.

The guard awaits connection.close(timeout=close_timeout) (5 s by default). Since 0.32.0, the timeout also covers the pending cancellation, and on timeout asyncpg aborts the socket. Before, the background close() on a silently dead connection could hang forever and keep the socket open.

Errors from close() are suppressed, so they never replace the original exception. Otherwise a TimeoutError from closing a dead connection swallows CancelledError, and the cancelled guard keeps running and reacquires the lock.

asyncpg 0.32.0 is required: with 0.31.0 the awaited close() hangs again, test_reacquire_lock_after_silent_disruption and the new tests fail.

Tests:

• test_release_silently_dead_connection: the guard drops a silently dead connection; fails on main, passes with the fix;
• test_stop_on_silently_dead_connection: the guard stops on cancellation while its connection is silently dead; passes on main, fails if close() errors are not suppressed.