Possible deadlock on DeferredConfirmation.Wait()

[ismurov]

Hi, there. 👋

I'm starting to migrate from github.com/streadway/amqp package and delve into the new features of this package. Currently I want to use the PublishWithDeferredConfirm method and it doesn't look production-ready to me. The case in which the problem occurs is closing the connection while waiting for publication confirmation from the AMQP server.

What I mean in more detail:
The type Channel has a shutdown method in which resources are cleared and closed, also here calls a Close method of confirms type. But this method does not properly clean up its resources such as deferredConfirmations an awaiting DeferredConfirmation.

dc, err := c.PublishWithDeferredConfirm(exchange, key, false, false, msg)
if err != nil {
	log.Fatalf("c.PublishWithDeferredConfirm: %s", err)
}
dc.Wait() // <- deadlock

Possible solution:
Add one more method in type deferredConfirmations and call it from confirms.Close.

// Close closes all awaiting DeferredConfirmation with Nack.
func (d *deferredConfirmations) Close() error {
	d.m.Lock()
	defer d.m.Unlock()

	for k, v := range d.confirmations {
		v.confirmation = Confirmation{DeliveryTag: k, Ack: false}
		v.wg.Done()
		delete(d.confirmations, k)
	}

	return nil
}

But it seems to me that such a situation should be handled with explicit error like ErrClosed. And it's breaking change of package API.

Package version: v1.3.0

[lukebakken]

Thank you for the report.

Possibly related to #10 and #14.

[shifengbin]

the same reason #44

[DanielePalaia]

PR44 and PR47 have been merged (#47). I will close this one. Keep us updated with a new Issue in case of other problems