In Go/Golang, authenticate all HTTP connections in one place (No code duplication)

http.go

package main

import "net/http"
import "io"
import "runtime"
import "log"

type authHandler func(http.ResponseWriter, *http.Request)

func allowed(r *http.Request) bool {
	return true
}

func (f authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !allowed(r) {
		w.WriteHeader(http.StatusForbidden)
		return
	}

	f(w, r)
}

func serveHello(w http.ResponseWriter, r *http.Request) {
	io.WriteString(w, "Hello World!\n")
}

func serveBye(w http.ResponseWriter, r *http.Request) {
	io.WriteString(w, "Bye World!\n")
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU() * 2)

	http.Handle("/hello", authHandler(serveHello))
	http.Handle("/bye", authHandler(serveBye))

	log.Fatal(http.ListenAndServe(":9000", nil))
}