simple reverse proxy service on gae

main.go

// date: 2019-07-12
// license: GPLv3 https://www.gnu.org/licenses/gpl-3.0.txt
// author: nanpuyue <nanpuyue@gmail.com> https://blog.nanpuyue.com

package main

import (
	"bufio"
	"golang.org/x/net/context"
	"google.golang.org/appengine"
	"google.golang.org/appengine/socket"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"
)

type Transport struct {
	Context context.Context
}

var _ http.RoundTripper = (*Transport)(nil)

func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
	conn, err := socket.DialTimeout(t.Context, "tcp", req.URL.Host, 10*time.Second)
	if err != nil {
		return nil, err
	}

	if err := req.Write(conn); err != nil {
		return nil, err
	}

	resp, err := http.ReadResponse(bufio.NewReader(conn), req)
	return resp, err
}

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		upstream, _ := url.Parse("http://example.com:80")

		r.Header.Add("X-Forwarded-For", r.RemoteAddr)

		proxy := httputil.NewSingleHostReverseProxy(upstream)
		proxy.Transport = &Transport{
			Context: appengine.NewContext(r),
		}
		proxy.ServeHTTP(w, r)
	})
	appengine.Main()
}