Not who you asked, but I have a similar setup. I can run everything I need for local development in that image (db, message queue emulator, cache, other services). So, setting things like environment variables or running postgres work the same as they do outside the container.

The image itself isn't the same image that the app gets deployed in, but is a portable dev environment with everything needed to build and run my apps baked in.

This comes with some nice side effects like being able to instantly spin up clean work environments on my laptop, someone elses, or a remote vm.