basic.go

package app

import (
	"encoding/base64"
	"net/http"
)

func Basic(username, password string) http.Handler {
	credential := base64.StdEncoding.EncodeToString([]byte(username + ":" + password))
	return &basicHandler{credential}
}

type basicHandler struct {
	credential string
}

func (bh *basicHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	credential := r.Header.Get("Authorization")
	if len(credential) <= 6 || credential[6:] != bh.credential {
		w.Header().Set("WWW-Authenticate", "Basic realm=\"Authorization Required\"")
		http.Error(w, "Not Authorized", http.StatusUnauthorized)
		return
	}
}

chain.go

package app

import (
	"net/http"
)

func Chain(handlers ...http.Handler) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		rw := newResponseWriter(w)
		for _, h := range handlers {
			h.ServeHTTP(rw, r)

			if rw.written {
				return
			}
		}
	}
}

func ChainFunc(handlers ...http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		rw := newResponseWriter(w)
		for _, h := range handlers {
			h(rw, r)

			if rw.written {
				return
			}
		}
	}
}

type responseWriter struct {
	http.ResponseWriter

	written bool
}

func newResponseWriter(w http.ResponseWriter) *responseWriter {
	return &responseWriter{w, false}
}

func (rw *responseWriter) Write(bs []byte) (int, error) {
	rw.written = true

	return rw.ResponseWriter.Write(bs)
}

func (rw *responseWriter) WriteHeader(i int) {
	rw.written = true

	rw.ResponseWriter.WriteHeader(i)
}