tokio-postgres handles this by just dispatching the "ROLLBACK" command in impl Drop and ignoring the response. https://github.com/rust-postgres/rust-postgres/blob/a7a49a90...

Is this not enough? What could go wrong? If the network connection dies or the task is cancelled, I'm assuming the database server cleans up the connection state and does a rollback automatically.

And adding async Drop will probably add a whole new set of footguns.