Using .tool-versions as go-version-file does not work

[hanseartic]

Description:
When using the action with

  with
    go-version-file: .tool-versions

it fails because the file is not being parsed correctly.

Action version:
v6.0.0

Platform:

• Ubuntu
• macOS
• Windows

Runner type:

• Hosted
• Self-hosted (only checked ubuntu-arm)

Tools version:
golang 1.25.3 (works when using go.mod)

Repro steps:

• Add a .tool-versions file to your go project:

  golang 1.25.3
  nodejs v22.21.1
  
  

  Or just add the golang directive – will fail as well.

• Make the workflow use this file:

  on:
    push:
      branches: [ '**' ]
  jobs:
    use_tool_versions:
      env:
        GOARCH: arm64
        GOOS: linux
      runs-on: ubuntu-24.04-arm
      permissions:
        contents: read
      steps:
        - uses: actions/checkout@v5
          with:
            fetch-depth: 0
        - name: Setup Go
          uses: actions/setup-go@v6
          with:
            go-version-file: .tool-versions
            cache-dependency-path: go.sum
        - name: Verify Go installation
          run: |
            go version
            echo "golang installed successfully from .tool-versions file"
  

• Trigger a run of the workflow

Expected behavior:
golang version from .tool-versions file (1.25.3) will be selected and installed.

Actual behavior:
The file seems to not be parsed correctly:

Run actions/setup-go@v6
  with:
    go-version-file: .tool-versions
    cache-dependency-path: go.sum
    check-latest: false
    token: ***
    cache: true
  env:
     <SHORTENED FOR READABILITY>
Setup go version spec golang 1.25.3
nodejs v22.21.1
Attempting to download golang 1.25.3
nodejs v22.21.1...
matching golang 1.25.3
nodejs v22.21.1...
Not found in manifest.  Falling back to download directly from Go
Error: Unable to find Go version 'golang 1.25.3
nodejs v22.21.1' for platform linux and architecture arm64.

Here is the link to an example run: https://github.com/hanseartic/setup-go-fails-with-tool-versions/actions/runs/19139275557
The same happens on self-hosted (which I can't share in a public repo).

[gowridurgad]

Hello @hanseartic,
Thank you for reporting this issue. We will investigate it and get back to you as soon as we have some feedback.