code: func (ch *Channel) NotifyCancel(c chan string) chan string {
  	ch.notifyM.Lock()
  	defer ch.notifyM.Unlock()
  
  	if ch.noNotify {
  		close(c)
  	} else {
  		ch.cancels = append(ch.cancels, c)
  	}
  
  	return c
  }
docs: /*
  NotifyCancel registers a listener for basic.cancel methods.  These can be sent
  from the server when a queue is deleted or when consuming from a mirrored queue
  where the master has just failed (and was moved to another node).
  
  The subscription tag is returned to the listener.
  
  */