forgot to call flag.Parse

main.go

@@ -24,6 +24,7 @@ func main() {
 		PrinterHostname: "http://" + hostname,
 		Port:            port,
 	}
+	flag.Parse()
 
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		if r.URL.Path == "index.html" || r.URL.Path == "/" {