Moodle on Heroku using S3 Bucket

Question

I'm trying to set up Moodle on a free Dyno on Heroku.

• I started my project with the stable version 3.10 of Moodle on a new repository.
• I've created the Heroku app and connected my github repository to it
• I've created an S3 Bucket that allows read and write access to objects from anyone

On config.php:

• I changed the database settings (to point to the free postgres database that I also created),
• I've set wwwroot as my Heroku app (http://myherokuappexample.herokuapp.com/)
• I've set dataroot as my S3 Bucket endpoint (https://mys3bucketnamexample.s3.eu-north-1.amazonaws.com/moodledata/)

I created the folder moodledata, added an image to it and I was able to access it from the browser (for example https://mys3bucketnamexample.s3.eu-north-1.amazonaws.com/moodledata/ola.png)

BUT I'm getting "Fatal error: $CFG->dataroot is not configured properly, directory does not exist or is not accessible! Exiting." when the app is deployed to Heroku.

What am I doing wrong?