code: func (r *Request) Reply(ok bool, payload []byte) error {
  	if !r.WantReply {
  		return nil
  	}
  
  	if r.ch == nil {
  		return r.mux.ackRequest(ok, payload)
  	}
  
  	return r.ch.ackRequest(ok)
  }
docs: // Reply sends a response to a request. It must be called for all requests
  // where WantReply is true and is a no-op otherwise. The payload argument is
  // ignored for replies to channel-specific requests.