...

// sending messages server
handler := http.DefaultServeMux
handler.HandleFunc("/sms", HandleWebhook(func(w http.ResponseWriter, b *Body) {

    msg := fmt.Sprintf("Grafana status: %s\n%s", b.Title, b.Message)
    sendMessage(msg)

}, 0))

go http.ListenAndServe(addr, handler)
log.Println(fmt.Sprintf("API is listening on: %s", addr))

...