setup-go/README.md

# setup-go

[![Basic validation](https://github.com/actions/setup-go/actions/workflows/basic-validation.yml/badge.svg)](https://github.com/actions/setup-go/actions/workflows/basic-validation.yml)
[![Validate 'setup-go'](https://github.com/actions/setup-go/actions/workflows/versions.yml/badge.svg)](https://github.com/actions/setup-go/actions/workflows/versions.yml)

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.

# V4

The V4 edition of the action offers:

 - Enabled caching by default

The action will try to enable caching unless the `cache` input is explicitly set to false.

Please see "[Caching dependency files and build outputs](https://github.com/actions/setup-go#caching-dependency-files-and-build-outputs)" for more information.

# V3

The V3 edition of the action offers:

- Adds `GOBIN` to the `PATH`
- Proxy support
- Check latest version
- Caching packages dependencies
- stable and oldstable aliases
- 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).

**Note:** The `setup-go` action uses executable binaries which are built by Golang side. The action does not build
golang from source code.

Matching by [semver spec](https://github.com/npm/node-semver):

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: '^1.13.1' # The Go version to download (if necessary) and use.
  - run: go version
```

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: '>=1.17.0'
  - run: go version
```

Matching an unstable pre-release:

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: '1.18.0-rc.1' # The Go version to download (if necessary) and use.
  - run: go version
```

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: '1.16.0-beta.1' # The Go version to download (if necessary) and use.
  - run: go version
```

# Usage

See [action.yml](action.yml)

## Basic

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    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@v3
  - uses: actions/setup-go@v4
    with:
      go-version: '1.14'
      check-latest: true
  - run: go run hello.go
```

## Using stable/oldstable aliases

If `stable` is provided, action will get the latest stable version from
the [`go-versions`](https://github.com/actions/go-versions/blob/main/versions-manifest.json) repository manifest.

If `oldstable` is provided, when current release is 1.19.x, action will resolve version as 1.18.x, where x is the latest
patch release.

**Note:** using these aliases will result in same version as using corresponding minor release with `check-latest` input
set to `true`

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: 'stable'
  - run: go run hello.go
```

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: 'oldstable'
  - run: go run hello.go
```

## Caching dependency files and build outputs:

The action has a built-in functionality for caching and restoring go modules and build outputs. It
uses [toolkit/cache](https://github.com/actions/toolkit/tree/main/packages/cache) under the hood but requires less configuration settings.
The `cache` input is optional, and caching is turned on by default.

The action defaults to search for the dependency file - go.sum in the repository root, and uses its hash as a part of
the cache key. Use `cache-dependency-path` input for cases when multiple dependency files are used, or they are located
in different subdirectories.

If some problem that prevents success caching happens then the action issues the warning in the log and continues the execution of the pipeline. 

**Caching in monorepos**

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version: '1.17'
      check-latest: true
      cache-dependency-path: subdir/go.sum
  - run: go run hello.go
  ```

## Getting go version from the go.mod file

The `go-version-file` input accepts a path to a `go.mod` file or a `go.work` file that contains the version of Go to be
used by a project. As the `go.mod` file contains only major and minor (e.g. 1.18) tags, the action will search for the
latest available patch version sequentially in the runner's directory with the cached tools, in
the [versions-manifest.json](https://github.com/actions/go-versions/blob/main/versions-manifest.json) file or at the go
servers.

If both the `go-version` and the `go-version-file` inputs are provided then the `go-version` input is used.
> The action will search for the `go.mod` file relative to the repository root

```yaml
steps:
  - uses: actions/checkout@v3
  - uses: actions/setup-go@v4
    with:
      go-version-file: 'path/to/go.mod'
  - run: go version
```

## 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@v3
      - name: Setup go
        uses: actions/setup-go@v4
        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-rc.2`, `1.16.0-beta.1`
- SemVer's version range syntax: `^1.13.1`, `>=1.18.0-rc.1`

For more information about semantic versioning, please refer to [semver](https://github.com/npm/node-semver)
documentation.

## Using `setup-go` on GHES

`setup-go` comes pre-installed on the appliance with GHES if Actions is enabled. When dynamically downloading Go
distributions, `setup-go` downloads distributions from [`actions/go-versions`](https://github.com/actions/go-versions)
on github.com (outside of the appliance). These calls to `actions/go-versions` are made via unauthenticated requests,
which are limited
to [60 requests per hour per IP](https://docs.github.com/en/rest/overview/resources-in-the-rest-api#rate-limiting). If
more requests are made within the time frame, then you will start to see rate-limit errors during downloading that looks
like: `##[error]API rate limit exceeded for...`. After that error the action will try to download versions directly
from https://storage.googleapis.com/golang, but it also can have rate limit so it's better to put token.

To get a higher rate limit, you
can [generate a personal access token on github.com](https://github.com/settings/tokens/new) and pass it as the `token`
input for the action:

```yaml
uses: actions/setup-go@v4
with:
  token: ${{ secrets.GH_DOTCOM_TOKEN }}
  go-version: '1.18'
```

If the runner is not able to access github.com, any Go versions requested during a workflow run must come from the
runner's tool cache.
See "[Setting up the tool cache on self-hosted runners without internet access](https://docs.github.com/en/enterprise-server@3.2/admin/github-actions/managing-access-to-actions-from-githubcom/setting-up-the-tool-cache-on-self-hosted-runners-without-internet-access)"
for more information.

# 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](CODE_OF_CONDUCT.md)