Closing PostgreSQL connection deadlocks listen(_:)

[billyean]

Describe the issue

Closing PostgreSQL connection deadlocks listen(_:)

Vapor version

latest

Operating system and version

macOS 26.01

Swift version

Swift 6.2

Steps to reproduce

Reproduction:

1. The code looks like that:

            try await self.postgresClient.withConnection { connection in
                148: log.debug("Notifications: Starting listening", metadata: [       
                    "topic": "\(topic)",                                         
                    "psql.conn.id": "\(connection.id)",                          
                    "psql.conn.isClosed": "\(connection.isClosed)"               
                ])                                                               
                sequence = try await connection.listen(topic.stringValue)        
                154: log.debug("Notifications: Now listening", metadata: [            
                    "topic": "\(topic)",                                          
                    "psql.conn.id": "\(connection.id)",                          
                    "psql.conn.isClosed": "\(connection.isClosed)"               
                ])
   

2. brew services restart postgresql

3. The error log similar to the log above gets generated, and the system goes into a deadlock.

Outcome

client goes to infinite waiting

Additional notes

Hash a PR for the fix #600

[billyean]

@fabianfett @gwynne can any of you review and push this?