Multiple host reverse proxy in Go

multiple-host-reverse-proxy.go

package main

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

var (
	hostTarget = map[string]string{
		"app1.domain.com": "http://192.168.1.2/owncloud",
		"app2.domain.com": "http://192.168.1.2:8080",
		"app3.domain.com": "http://192.168.1.2:8888",
	}
	hostProxy map[string]*httputil.ReverseProxy = map[string]*httputil.ReverseProxy{}
)

type baseHandle struct{}

func (h *baseHandle) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	host := r.Host

	if fn, ok := hostProxy[host]; ok {
		fn.ServeHTTP(w, r)
		return
	}

	if target, ok := hostTarget[host]; ok {
		remoteUrl, err := url.Parse(target)
		if err != nil {
			log.Println("target parse fail:", err)
			return
		}

		proxy := httputil.NewSingleHostReverseProxy(remoteUrl)
		hostProxy[host] = proxy
		proxy.ServeHTTP(w, r)
		return
	}
	w.Write([]byte("403: Host forbidden " + host))
}

func main() {

	h := &baseHandle{}
	http.Handle("/", h)

	server := &http.Server{
		Addr:    ":8082",
		Handler: h,
	}
	log.Fatal(server.ListenAndServe())
}

to prevent Golang compiler from giving you a panic error, change line 16 to hostProxy = make(map[string]*httputil.ReverseProxy)

I'm new to reverse proxy. how do I test these?

small diff, change line 16 to:

	hostProxy map[string]*httputil.ReverseProxy = map[string]*httputil.ReverseProxy{}

New to Golang here - how does this line work? It should kill the process shouldn't it?

log.Fatal(server.ListenAndServe())

New to Golang here - how does this line work? It should kill the process shouldn't it?

log.Fatal(server.ListenAndServe())

It should just listen and serve just like http.ListenAndServe(). It should serve http handlers, run indefinitely, and stop from either a graceful shutdown or an unexpected error