code: func (s *Spec) GetCode(msg interface{}) (uint64, bool) {
  	s.init()
  	typ := reflect.TypeOf(msg)
  	if typ.Kind() == reflect.Ptr {
  		typ = typ.Elem()
  	}
  	code, ok := s.codes[typ]
  	return code, ok
  }
docs: // GetCode returns the message code of a type, and boolean second argument is
  // false if the message type is not found