Allow setting Go version from go.mod file

[bewuethr]

setup-go supports setting the Go version from the go.mod file; for Go 1.20 and older, it'll use the latest cached patch version on the same minor version, and for Go 1.21+, it'll use the exact version from go.mod, which now also includes the patch version.

Would it be possible to expose the go-version-file input in gh-extension-precompile as well? I previously extracted the Go version in a separate run step with go mod edit -json | jq -r '.Go', but that breaks if go.mod uses 1.21.0 or later, since the default Go on Actions runners, 1.20.8, considers the go.mod incorrectly formatted. I now use awk, which is less robust, but it would be nice to just leverage the existing setup-go functionality.

Happy to create a PR for this if there's interest, potentially including the check-latest flag from setup-go as well.

[samcoe]

@bewuethr Exposing a go-version-file input that goes directly to setup-go action makes sense to me, we would be open to a PR for the feature. Let's hold off on check-latest input though as the team would like more time to think on if we want to support that.

[andyfeller]

Having done this for another GitHub Action, I thought I'd share the solution we ended up with:

inputs:
  go-version:
    description: The version of go to use.
    required: false
  go-version-file:
    description: Path to the go.mod or go.work file to determine version of go to use
    required: false
runs:
  using: composite
  steps:
    - name: Setup Go
      uses: actions/setup-go@v4
      with:
        # The default go version is managed here because actions/setup-go favors go-version over go-version-file,
        # requiring us to only pass it if no other inputs are provided.
        #
        # Otherwise, we pass along the values given, letting the user catch the warning notice in the logs
        # and picking either go-version or go-version-file.
        go-version: ${{(inputs.go-version-file == '' && inputs.go-version == '') && '1.20' || inputs.go-version}}
        go-version-file: ${{inputs.go-version-file}}

In keeping with actions/setup-go, the go-version input will be favored over go-version-file if both are provided. If neither are provided, then the 1.20 within the expression will be used.

[bewuethr]

In keeping with actions/setup-go, the go-version input will be favored over go-version-file if both are provided. If neither are provided, then the 1.20 within the expression will be used.

Couldn't you use 1.20 as the default for inputs.go-version, and then pass through both values directly, no additional expressions required? Something like

inputs:
  go-version:
    description: The version of go to use.
    required: false
    default: '1.20'
  go-version-file:
    description: Path to the go.mod or go.work file to determine version of go to use
    required: false
runs:
  using: composite
  steps:
    - name: Setup Go
      uses: actions/setup-go@v4
      with:
        go-version: ${{ inputs.go-version }}
        go-version-file: ${{ inputs.go-version-file }}

[andyfeller]

So the problem is that go-version always takes precedence from actions/setup-go. So if you pass in go.mod for go-version-file, it won't pick it up because the input default value will always be passed in. Thus, we have to do some silly conditional hackery like this to only pass 1 value in when one is set.

[andyfeller]

created #47 for this