slash.go

http.HandleFunc("/slash", func(w http.ResponseWriter, r *http.Request) {
	s, err := slack.SlashCommandParse(r)
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	if !s.ValidateToken(verificationToken) {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}

	switch s.Command {
	case "/echo":
		params := &slack.Msg{Text: s.Text}
		b, err := json.Marshal(params)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.Write(b)
	default:
		w.WriteHeader(http.StatusInternalServerError)
		return
	}
})
fmt.Println("[INFO] Server listening")
http.ListenAndServe(":3000", nil)