code: func validateRequest(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
  	devFlag := r.URL.Query().Get("_dev")
  	isDev := devFlag != ""
  	if !isDev && !IsValidAlexaRequest(w, r) {
  		log.Println("Request invalid")
  		return
  	}
  	next(w, r)
  }
docs: // Run all mandatory Amazon security checks on the request.