Django not finding environment variables set by Github Actions

Question

I have a Github Action that creates a Docker image, and the issue I am having is that when I docker logs backend I get an error like:

File "/usr/src/app/api/settings/common.py", line 165, in <module>
    AWS_ACCESS_KEY_ID = os.environ["AWS_ACCESS_KEY_ID"]
  File "/usr/local/lib/python3.9/os.py", line 679, in __getitem__
    raise KeyError(key) from None
KeyError: 'AWS_ACCESS_KEY_ID'

As part of my .yml for GitHub I have this code which from research should inject the environment variables into my Docker image.

jobs:
  build_and_deploy_backend__production:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout the repo
        uses: actions/checkout@v2

      - name: Build image
        run: docker build -t backend .
        env:
          AWS_ACCESS_KEY_ID: ${{ secrets.GLOBAL_AWS_ACCESS_KEY_ID }}
          AWS_SECRET_ACCESS_KEY: ${{ secrets.GLOBAL_AWS_SECRET_ACCESS_KEY }}

I am wondering if there is anything obvious that I am doing wrong.