code: func NewClientCodec(conn io.ReadWriteCloser) rpc.ClientCodec {
  	return &clientCodec{
  		dec:     json.NewDecoder(conn),
  		enc:     json.NewEncoder(conn),
  		c:       conn,
  		pending: make(map[uint64]string),
  	}
  }
docs: // NewClientCodec returns a new rpc.ClientCodec using JSON-RPC on conn.