code: func (msg *MsgAlert) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) error {
  	var err error
  
  	msg.SerializedPayload, err = ReadVarBytes(r, pver, MaxMessagePayload,
  		"alert serialized payload")
  	if err != nil {
  		return err
  	}
  
  	msg.Payload, err = NewAlertFromPayload(msg.SerializedPayload, pver)
  	if err != nil {
  		msg.Payload = nil
  	}
  
  	msg.Signature, err = ReadVarBytes(r, pver, MaxMessagePayload,
  		"alert signature")
  	return err
  }
docs: // BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
  // This is part of the Message interface implementation.