code: function slackSlashCommand(req, res, next) {
    if (req.body.command === '/interactive-example') {
      const type = req.body.text.split(' ')[0];
      if (type === 'button') {
        res.json(interactiveButtons);
      } else if (type === 'menu') {
        res.json(interactiveMenu);
      } else if (type === 'dialog') {
        res.send();
        web.dialog.open({
          trigger_id: req.body.trigger_id,
          dialog,
        }).catch((error) => {
          return axios.post(req.body.response_url, {
            text: `An error occurred while opening the dialog: ${error.message}`,
          });
        }).catch(console.error);
      } else {
        res.send('Use this command followed by `button`, `menu`, or `dialog`.');
      }
    } else {
      next();
    }
  }
docs: Slack slash command handler