App relies on sourcing for env variables. How to accomplish this in my Dockerfile?

I’m working on creating a container to hold my running Django app. During development and manual deployment I’ve been setting environment variables by sourcing a file in my repo. This has worked fine until now that I’m trying to automate my server’s configuration environment in a Dockerfile.

So far it looks like this:

FROM python:3.7-alpine

RUN pip install --upgrade pip
RUN pip install pipenv

RUN addgroup -S appgroup && adduser -S appuser -G appgroup

USER appuser

WORKDIR /home/appuser/site

COPY . /home/appuser/site

RUN /bin/sh -c "source"
RUN env

I’d expect this to set the environment variables properly but it doesn’t. I’ve also tried adding the variables to my appuser’s bashrc, but this doesn’t work either.

Am I missing something here? Is there another best practice to set env variables to be accessible by django, without having to check them into the Dockerfile in my repo?

Source: StackOverflow