code: func (msg *Message) SetExpectedMsgID(id string) error {
  	if msg.Type() != "reply" {
  		return fmt.Errorf("can only store expected message ID for reply messages")
  	}
  
  	msg.expectedMessageID = id
  
  	return nil
  }
docs: // SetExpectedMsgID sets the Request ID that is expected from the reply data