code: func (s *Server) RPC(method string, args interface{}, reply interface{}) error {
  	codec := &inmemCodec{
  		method: method,
  		args:   args,
  		reply:  reply,
  	}
  	if err := s.rpcServer.ServeRequest(codec); err != nil {
  		return err
  	}
  	return codec.err
  }
docs: // RPC is used to make a local RPC call