Simple reverse proxy in Go - Prints forwarded addresses

revprox.go

package main

import (
	"bytes"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"
)

func toJson(r *http.Request) *bytes.Buffer {
	var out string
	out += "{"
	if r.Header.Get("X-Forwarded-For") != "" {
		out += "\"X-Forwarded-For\":\""
		out += r.Header.Get("X-Forwarded-For")
		out += "\","
	}
	if r.URL.Path != "" {
		out += "\"GET\":\""
		out += r.URL.Path
		out += "\","
	}
	if r.URL.Host != "" {
		out += "\"Host\":\""
		out += r.URL.Host
		out += "\","
	}
	if r.Header.Get("CF-IPCountry") != "" {
		out += "\"CF-IPCountry\":\""
		out += r.Header.Get("CF-IPCountry")
		out += "\","
	}
	if r.Header.Get("user-agent") != "" {
		out += "\"user-agent\":\""
		out += r.Header.Get("user-agent")
		out += "\","
	}
	out += "\"time\":\""
	out += time.Now().String() + "\""
	out += "}"
	log.Println(out)
	return bytes.NewBufferString(out)
}

func main() {
	remote, err := url.Parse("http://127.0.0.1:81")
	if err != nil {
		panic(err)
	}

	proxy := httputil.NewSingleHostReverseProxy(remote)
	http.HandleFunc("/", handler(proxy))
	err = http.ListenAndServe(":80", nil)
	if err != nil {
		panic(err)
	}
}

func handler(p *httputil.ReverseProxy) func(http.ResponseWriter, *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		_, err := http.Post("http://localhost:9200/gatling/request/?pretty", "application/json", toJson(r))
		if err != nil {
			panic(err)
		}
		p.ServeHTTP(w, r)
	}
}