setup-go/README.md

# setup-go

<p align="left">
  <a href="https://github.com/actions/setup-go/actions"><img alt="GitHub Actions status" src="https://github.com/actions/setup-go/workflows/build-test/badge.svg"></a>

  <a href="https://github.com/actions/setup-go/actions"><img alt="versions status" src="https://github.com/actions/setup-go/workflows/go-versions/badge.svg"></a>  
</p>

This action sets up a go environment for use in actions by:

- optionally downloading and caching a version of Go by version and adding to PATH
- registering problem matchers for error output

# V2

The V2 offers:
- Adds GOBIN to the PATH
- Proxy Support
- `stable` input 
- Check latest version
- Bug Fixes (including issues around version matching and semver)

The action will first check the local cache for a version match. If a version is not found locally, it will pull it from the `main` branch of the [go-versions](https://github.com/actions/go-versions/blob/main/versions-manifest.json) repository. On miss or failure, it will fall back to downloading directly from [go dist](https://storage.googleapis.com/golang). To change the default behavior, please use the [check-latest input](#check-latest-version).

Matching by [semver spec](https://github.com/npm/node-semver):
```yaml
steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-go@v2
    with:
      go-version: '^1.13.1' # The Go version to download (if necessary) and use.
  - run: go version
```

Matching an unstable pre-release:
```yaml
steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-go@v2
    with:
      stable: 'false'
      go-version: '1.14.0-rc1' # The Go version to download (if necessary) and use.
  - run: go version
```

# Usage

See [action.yml](action.yml)

## Basic:
```yaml
steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-go@v2
    with:
      go-version: '1.16.1' # The Go version to download (if necessary) and use.
  - run: go run hello.go
```


## Check latest version:  

The `check-latest` flag defaults to `false`. Use the default or set `check-latest` to `false` if you prefer stability and if you want to ensure a specific Go version is always used.

If `check-latest` is set to `true`, the action first checks if the cached version is the latest one. If the locally cached version is not the most up-to-date, a Go version will then be downloaded. Set `check-latest` to `true` if you want the most up-to-date Go version to always be used.

> Setting `check-latest` to `true` has performance implications as downloading Go versions is slower than using cached versions.

```yaml
steps:
  - uses: actions/checkout@v2
  - uses: actions/setup-go@v2
    with:
      go-version: '1.14'
      check-latest: true
  - run: go run hello.go
```

## Matrix Testing:
```yaml
jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        go: [ '1.14', '1.13' ]
    name: Go ${{ matrix.go }} sample
    steps:
      - uses: actions/checkout@v2
      - name: Setup go
        uses: actions/setup-go@v2
        with:
          go-version: ${{ matrix.go }}
      - run: go run hello.go
```

### Supported version syntax
The `go-version` input supports the following syntax:

Specific versions: `1.15`, `1.16.1`, `1.17.0-rc2`, `1.16.0-beta1`  
SemVer's version range syntax: `^1.13.1`  
For more information about semantic versioning please refer [semver](https://github.com/npm/node-semver) documentation

# License

The scripts and documentation in this project are released under the [MIT License](LICENSE)

# Contributions

Contributions are welcome!  See [Contributor's Guide](docs/contributors.md)

## Code of Conduct

:wave: Be nice.  See [our code of conduct](CONDUCT)