func Hello(w http.ResponseWriter, r *http.Request) { log.Println("%s called /", r.Host) w.Header().Set("Content-Type", "text/html") ifaces, _ := net.Interfaces() var ip net.IP for _, i := range ifaces { addrs, _ := i.Addrs() for _, addr := range addrs { switch v := addr.(type) { case *net.IPNet: ip = v.IP case *net.IPAddr: ip = v.IP } } } b, _ := ip.MarshalText() res := fmt.Sprintf("<div style='text-align:center;'><p style='font-size:5em'>%s</p><p style='font-size:3em'>v2.0</p></div>", b) w.Write([]byte(res)) }