Buildkite Docker Plugin v2.0.0 has been released, and includes:

• Support for multi-line commands
• A new command option for using single-binary/command line Docker images
• Windows container support

steps:
  - command: 'dotnet publish -c Release -o published'
    plugins:
      - docker#v2.0.0:
          image: 'microsoft/dotnet:latest'
          always-pull: true

See all the details, and upgrade instructions, on the release notes: https://github.com/buildkite-plugins/docker-buildkite-plugin/releases/tag/v2.0.0