code: func (d Delivery) Nack(multiple, requeue bool) error {
  	if d.Acknowledger == nil {
  		return errDeliveryNotInitialized
  	}
  	return d.Acknowledger.Nack(d.DeliveryTag, multiple, requeue)
  }
docs: /*
  Nack negatively acknowledge the delivery of message(s) identified by the
  delivery tag from either the client or server.
  
  When multiple is true, nack messages up to and including delivered messages up
  until the delivery tag delivered on the same channel.
  
  When requeue is true, request the server to deliver this message to a different
  consumer.  If it is not possible or requeue is false, the message will be
  dropped or delivered to a server configured dead-letter queue.
  
  This method must not be used to select or requeue messages the client wishes
  not to handle, rather it is to inform the server that the client is incapable
  of handling this message at this time.
  
  Either Delivery.Ack, Delivery.Reject or Delivery.Nack must be called for every
  delivery that is not automatically acknowledged.
  */