How to go into production?

Yes. You may need to add a step to make your site maintenance mode.
But if it would takes long time, you may want to run migrations manually.

If you want to rollback when something wrong happens,
1. update your app code to work with both before and after migrations.
2. deploy the app.
3. add migrations.
4. deploy the app (run migrations).

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper