docker-compose: help configure django use postgres instead of sqlite

I am using docker-compose to build a containerised application, but can't get django to use postgres instead of sqlite in despite of having configured settings.py (when authenticating with /admin, it's throwing sqlite errors), but manage.py migrate ran corrrectly on postgres as it generated the tables

packages/django/db/backends/sqlite3/base.py", line 423, in execute

return Database.Cursor.execute(self, query, params)

django.db.utils.OperationalError: no such table: auth_user