A simple HTTP server in Golang which just prints all the headers

print-headers-401.go

package main

import (
	"net/http"
	"fmt"
	"time"
)

func handler(w http.ResponseWriter, r *http.Request) {
	fmt.Printf("Request at %v\n", time.Now())
	for k, v := range r.Header {
		fmt.Printf("%v: %v\n", k, v)
	}

	if r.Header.Get("Authorization") == "" {
		w.WriteHeader(http.StatusUnauthorized)
		w.Header().Set("WWW-Authenticate", `Digest realm="[email protected]", qop="auth,auth-int", nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093", opaque="5ccc069c403ebaf9f0171e9517f40e41"`)
	}
}

func main() {
	http.HandleFunc("/", handler)
	http.ListenAndServe(":9090", nil)
}

print-headers.go

package main

import (
	"net/http"
	"fmt"
	"time"
)

func handler(w http.ResponseWriter, r *http.Request) {
	fmt.Printf("Request at %v\n", time.Now())
	for k, v := range r.Header {
		fmt.Printf("%v: %v\n", k, v)
	}
}

func main() {
	http.HandleFunc("/", handler)
	http.ListenAndServe(":9090", nil)
}

The example is unfortunately incorrect. The order of w.WriteHeader(http.StatusUnauthorized) and w.Header().Set("WWW-Authenticate", ... should be swapped:

  // first set header
  w.Header().Set("WWW-Authenticate", ...)
  // then write (send) the headers
  w.WriteHeader(http.StatusUnauthorized)