server.go w/ HTTP/2 proxy issues: golang/go, Issue #16788 - https://github.com/golang/go/issues/16788

simple.go

package main

import (
	"flag"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"

	"log"
)

// Rev is the git revision set by -ldflags
var Rev string

type config struct {
	Bundled bool
	Entry   string
	Host    string
	Port    string
	Proxy   string
	Static  string
}

func main() {
	conf, err := parseConfig()
	if err != nil {
		log.Fatal(err)
	}

	r := http.NewServeMux()

	// Proxy calls to the CloudFlare API.
	target, err := url.Parse(conf.Proxy)
	if err != nil {
		log.Fatal(err)
	}

	proxy := httputil.NewSingleHostReverseProxy(target)
	proxy.Director = func(r *http.Request) {
		r.Host = target.Host
		r.URL.Scheme = target.Scheme
		r.URL.Host = target.Host
		log.Printf("%s - %s - %s", r.Method, r.URL.String(), r.RemoteAddr)
	}

	r.Handle("/", proxy)

	srv := &http.Server{
		Handler:      r,
		Addr:         conf.Host + ":" + conf.Port,
		WriteTimeout: 15 * time.Second,
		ReadTimeout:  15 * time.Second,
	}

	log.Printf("listening on host %s - port %s", conf.Host, conf.Port)
	log.Fatal(srv.ListenAndServe())
}

func parseConfig() (*config, error) {
	conf := &config{}

	flag.StringVar(&conf.Entry,
		"entry",
		"./dist/index.html",
		"the entrypoint to serve.")
	flag.StringVar(&conf.Static,
		"static",
		"./dist/static",
		"the directory to serve static files from.")
	flag.StringVar(&conf.Proxy,
		"proxy",
		"https://api.cloudflare.com/client/v4/",
		"the URL to `proxy` to")
	flag.StringVar(&conf.Host,
		"host",
		"127.0.0.1",
		"the `host` to listen on.")
	flag.StringVar(&conf.Port,
		"port",
		"8000",
		"the `port` to listen on.")
	flag.BoolVar(&conf.Bundled,
		"bundled",
		false,
		"`bundled` will use assets bundled into the binary")
	flag.Parse()

	return conf, nil
}

func IndexHandler(entrypoint string) func(w http.ResponseWriter, r *http.Request) {
	fn := func(w http.ResponseWriter, r *http.Request) {
		http.ServeFile(w, r, entrypoint)
	}

	return http.HandlerFunc(fn)
}