Send WWW-Authenticate along with 401 for RFC 7235 conformity

main.go

@@ -148,6 +148,7 @@ func main() {
 	http.HandleFunc("/departures", func(w http.ResponseWriter, r *http.Request) {
 		user, pass, ok := r.BasicAuth()
 		if !(ok && user == "admin" && pass == password) {
+			w.Header().Set("WWW-Authenticate", "Basic realm=\"Access to departure API\"")
 			http.Error(w, "You shall not pass", http.StatusUnauthorized)
 			return
 		}