code: func (s *Server) handlePOST(c *router.Context) {
  	serviceName := c.Params.ByName("service")
  	methodName := c.Params.ByName("method")
  	s.setAccessControlHeaders(c, false)
  	res := s.call(c, serviceName, methodName)
  	if res.err != nil {
  		writeError(c.Context, c.Writer, res.err)
  		return
  	}
  	writeMessage(c.Context, c.Writer, res.out, res.fmt)
  }
docs: // handle handles RPCs.
  // See https://godoc.org/go.chromium.org/luci/grpc/prpc#hdr-Protocol
  // for pRPC protocol.