Why dotenv is not loaded in docker but works fine in host machine?
I think this is caused by:
volumes: - ".:/usr/src/app"in your docker-compose file. This links the current dir to the app folder, meaning everything including node_modules is replaced.
Try removing the volumes from docker-compose and see if it works.
When you run docker run -it myimage /bin/sh it will not link the volume, meaning it will be using the correct node_modules, which is why it works when using that.