It's the official GitHub action for golangci-lint from it's authors. The action runs golangci-lint and reports issues from linters.

Add .github/workflows/golangci-lint.yml with the following contents:

name: golangci-lint
on:
  push:
    tags:
      - v*
    branches:
      - master
  pull_request:
jobs:
  golangci:
    name: lint
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: golangci-lint
        uses: golangci/golangci-lint-action@v1
        with:
          # Required: the version of golangci-lint is required and must be specified without patch version: we always use the latest patch version.
          version: v1.26
          
          # Optional: working directory, useful for monorepos
          # working-directory: somedir

          # Optional: golangci-lint command line arguments.
          # args: --issues-exit-code=0

          # Optional: show only new issues if it's a pull request. The default value is `false`.
          # only-new-issues: true

We recommend running this action in a job separate from other jobs (go test, etc) because different jobs run in parallel.

Currently, GitHub parses the action's output and creates annotations.

The restrictions of annotations are the following:

1. Currently, they don't support markdown formatting (see the feature request)
2. They aren't shown in list of comments like it was with golangci.com. If you would like to have comments - please, up-vote the issue.

The action was implemented with performance in mind:

1. We cache data by @actions/cache between builds: Go build cache, Go modules cache, golangci-lint analysis cache.
2. We don't use Docker because image pulling is slow.
3. We do as much as we can in parallel, e.g. we download cache, go and golangci-lint binary in parallel.

For example, in a repository of golangci-lint running this action without the cache takes 50s, but with cache takes 14s:

• in parallel:
  • 13s to download Go
  • 4s to restore 50 MB of cache
  • 1s to find and install golangci-lint
• 1s to run golangci-lint (it takes 35s without cache)

We use JavaScript-based action. We don't use Docker-based action because:

1. docker pulling is slow currently
2. it's easier to use caching from @actions/cache

Inside our action we perform 3 steps:

1. Setup environment running in parallel:

• restore cache of previous analyzes
• fetch action config and find the latest golangci-lint patch version for needed version (users of this action can specify only minor version of golangci-lint). After that install golangci-lint using @actions/tool-cache
• install the latest Go 1.x version using @actions/setup-go

2. Run golangci-lint with specified by user args
3. Save cache for later builds

1. We save and restore the following directories: ~/.cache/golangci-lint, ~/.cache/go-build, ~/go/pkg.
2. The primary caching key looks like golangci-lint.cache-{interval_number}-{go.mod_hash}. Interval number ensures that we periodically invalidate our cache (every 7 days). go.mod hash ensures that we invalidate the cache early - as soon as dependencies have changed.
3. We use restore keys: golangci-lint.cache-{interval_number}-, golangci-lint.cache-. GitHub matches keys by prefix if we have no exact match for the primary cache.

This scheme is basic and needs improvements. Pull requests and ideas are welcome.

1. Install act
2. Make a symlink for act to work properly: ln -s . golangci-lint-action
3. Prepare deps once: npm run prepare-deps
4. Run npm run local after any change to test it