Not receiving response from button click

[NearlyUnique]

I'm porting a bot over from Slack Bolt with javascript for "reasons".
The code responds to a slack command. Developing locally using ngrok.
The UI appears in Slack however the subsequent button click generates a client error 404 not found, a request to Slack can be observed in the browser dev tools, however no request is seen in ngrok or sent to my app

Smallest reproduction I could manage, this code generates the UI as expected. The button click generates a 404, which I understand is a generic "this didn't work" message from Slack.

func main() {
	mux := http.NewServeMux()
	mux.Handle("/slack/events", githubSlackHandler(os.Getenv("SlackSigningSecret"), os.Getenv("SlackBotToken")))
	srv := &http.Server{
		Addr:    ":3000",
		Handler: mux,
	}
	if err := srv.ListenAndServe(); err != nil {
		panic(err)
	}
}
func githubSlackHandler(signingSecret, botToken string) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		cmd, err := slack.SlashCommandParse(r)
		if err != nil {
			panic(err)
		}
		api := slack.New(botToken)
		api.PostMessage(cmd.ChannelID,
			slack.MsgOptionBlocks(
				slack.NewActionBlock(
					"my_app_response_actions",
					slack.NewButtonBlockElement(
						"click_btn", "clicked",
						slack.NewTextBlockObject("plain_text", "click button", false, false),
					))),
		)
	})
}

[nlopes]

Hey hey. Can you confirm you have this section set up?

Basically, if you don't have a url set in this section, Slack has no place to send your interactivity.

[NearlyUnique]

Thanks you. I can't really tell if this fixed it as I put down the go implementation for a while and quite a lot of config may have changed but this is now configured and this works as described.

[nlopes]

No worries, thank you for getting back to me.