code: func (server *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
  	if req.Method != "CONNECT" {
  		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
  		w.WriteHeader(http.StatusMethodNotAllowed)
  		io.WriteString(w, "405 must CONNECT\n")
  		return
  	}
  	conn, _, err := w.(http.Hijacker).Hijack()
  	if err != nil {
  		log.Print("rpc hijacking ", req.RemoteAddr, ": ", err.Error())
  		return
  	}
  	io.WriteString(conn, "HTTP/1.0 "+connected+"\n\n")
  	server.ServeConn(conn)
  }
docs: // ServeHTTP implements an http.Handler that answers RPC requests.