Describe the bug
I am unable to refer to environment variables using the ${{env.name} syntax. More specifically, the environment variable ImageOS that is automatically created by Github when running a workflow.

Version

• V1
• V2

Environment

• self-hosted
• Linux
• Windows
• Mac

Screenshots
Usage:

    - name: Archive installation packages
      uses: actions/upload-artifact@v2
      with:
        name: bin2cpp-packages-${{env.ImageOS}}
        path: build/bin2cpp-${{env.BIN2CPP_VERSION}}-*.*

Output:

Run actions/upload-artifact@v2
  with:
    name: bin2cpp-packages-
    path: build/bin2cpp-2.4.0-*.*
    if-no-files-found: warn
  env:
    PlatformToolset: v140
    Platform: x64
    Configuration: Release
    pythonLocation: C:\hostedtoolcache\windows\Python\3.9.5\x64
    GIT_REPOSITORY: bin2cpp
    GIT_BRANCH: master
    GITHUB_WORKFLOW: Windows
    UNITTEST_REPORT_PATH: D:\a\bin2cpp\bin2cpp\build\bin\Release\bin2cpp_unittest.x64.release.xml
    BIN2CPP_VERSION: 2.4.0

Run/Repo Url
Repo: https://github.com/end2endzone/bin2cpp
Workflow runs: macos, linux and windows

How to reproduce
I call the action as specified above in "usage". Looking at the output, we see that name is resolved as bin2cpp-packages- instead of the expected string bin2cpp-packages-ubuntu20. It is missing the ${{env.ImageOS}} concatenation. I was under the impression that I could refer to any environment variables as specified in your readme here but in your example, name might be a custom variable.

Additional context
Looking at the "usage" reference above, I am able to refer to my "custom" environment variable BIN2CPP_VERSION without a problem. This variable is created manually in a previous step with something like echo BIN2CPP_VERSION=2.4.0 >> $GITHUB_ENV. However, I am unable to reference other environment variables such as the one provided by Github Actions.

I was able to confirm that ImageOS environment is actually created using the following action in Linux and macOS :

    - name: List environment variables for debugging
      working-directory: ${{env.GITHUB_WORKSPACE}}
      shell: bash
      run: |
        env

or on Windows,

    - name: List environment variables for debugging
      working-directory: ${{env.GITHUB_WORKSPACE}}
      shell: cmd
      run: |
        set

Note: This issue seems to be related to #216 but I am not certain thus creating a new issue. #216 is about specific docker variables which I do not use.