docker:

docker: URL scheme

[1] GitHub Actionsのワークフロー構文 - GitHub Docs (2021-10-05T06:27:57.000Z) https://docs.github.com/ja/actions/learn-github-actions/workflow-syntax-for-github-actions#example-using-status-check-functions

[2] Workflow syntax for GitHub Actions - GitHub Docs (2022-04-08T03:06:21.000Z) https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#example-using-a-docker-hub-action

docker://{image}:{tag}

[3] Workflow syntax for GitHub Actions - GitHub Docs (2022-04-08T03:06:35.000Z) https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#example-using-a-docker-hub-action

docker://{host}/{image}:{tag}