code: func (msg *MsgPing) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) error {
  	// There was no nonce for BIP0031Version and earlier.
  	// NOTE: > is not a mistake here.  The BIP0031 was defined as AFTER
  	// the version unlike most others.
  	if pver > BIP0031Version {
  		err := readElement(r, &msg.Nonce)
  		if err != nil {
  			return err
  		}
  	}
  
  	return nil
  }
docs: // BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
  // This is part of the Message interface implementation.