Run entire GitHub Actions workflow job in private docker container

Question

I am trying to use the container option in a GitHub Actions workflow to run the entire job in a docker container. How do I specify the login credentials to retrieve this docker image from a private repository on docker hub?

jobs:
  build:
    runs-on: ubuntu-18.04
    container: private_org/test-runner:1.0

I have successfully used the following docker-login "action" to authenticate with docker hub as a "step", but this does not get performed until after the job-level container gets initialized.

jobs:
  build:
    runs-on: ubuntu-18.04
    steps:
    - uses: azure/docker-login@v1
      with:
        username: me
        password: ${{ secrets.MY_DOCKERHUB_PASSWORD }}
    - name: test docker creds
      run: docker pull private_org/test-runner:1.0

Answer 1

This was implemented recently. Use the following workflow definition:

jobs:
  build:
    container:
      image: private_org/test-runner:1.0
      credentials:
        username: me
        password: ${{ secrets.MY_DOCKERHUB_PASSWORD }}

Source: https://github.blog/changelog/2020-09-24-github-actions-private-registry-support-for-job-and-service-containers/