No need to close NATS receiver channel.

Will be garbage collected once the room is removed and is not needed to
wakeup the reader (which is terminated in a "select" loop from the close
channel).

room.go

@@ -180,7 +180,6 @@ func (r *Room) unsubscribeBackend() {
 		if err := subscription.Unsubscribe(); err != nil {
 			log.Printf("Error closing backend subscription for room %s: %s", r.Id(), err)
 		}
-		close(r.natsReceiver)
 	}(r.backendSubscription)
 	r.backendSubscription = nil
 }