GitHub Actions CI/CD Skill

Workflow File Location

All workflows live in .github/workflows/ as YAML files.

Step 1: Core Syntax

# .github/workflows/ci.yml
name: CI

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

jobs:
  test:
    name: Test
    runs-on: ubuntu-latest  # or: ubuntu-22.04, windows-latest, macos-latest

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Set up Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Run lint
        run: npm run lint

      - name: Run tests
        run: npm test -- --coverage

Step 2: Language-Specific Setup

Python

    - name: Set up Python
      uses: actions/setup-python@v5
      with:
        python-version: '3.12'
        cache: 'pip'

    - name: Install dependencies
      run: pip install -r requirements.txt -r requirements-dev.txt

    - name: Lint with ruff
      run: ruff check .

    - name: Type check with mypy
      run: mypy .

    - name: Run tests
      run: pytest --cov=. --cov-report=xml

    - name: Upload coverage
      uses: codecov/codecov-action@v4
      with:
        token: ${{ secrets.CODECOV_TOKEN }}

Go

    - name: Set up Go
      uses: actions/setup-go@v5
      with:
        go-version: '1.22'
        cache: true

    - name: Download dependencies
      run: go mod download

    - name: Run vet
      run: go vet ./...

    - name: Run tests
      run: go test -race -coverprofile=coverage.out ./...

Step 3: Matrix Builds

Test across multiple versions simultaneously:

jobs:
  test:
    strategy:
      fail-fast: false  # don't cancel others if one fails
      matrix:
        node-version: ['18', '20', '22']
        os: [ubuntu-latest, windows-latest]

    runs-on: ${{ matrix.os }}

    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: ${{ matrix.node-version }}
      - run: npm ci
      - run: npm test

Step 4: Dependency Caching

# Node.js - built into setup-node
- uses: actions/setup-node@v4
  with:
    node-version: '20'
    cache: 'npm'      # or 'yarn', 'pnpm'

# Python - built into setup-python
- uses: actions/setup-python@v5
  with:
    python-version: '3.12'
    cache: 'pip'

# Manual cache for arbitrary files
- uses: actions/cache@v4
  with:
    path: |
      ~/.cache/pip
      ~/.cargo/registry
    key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements*.txt') }}
    restore-keys: |
      ${{ runner.os }}-pip-

Step 5: Secrets and Environment Variables

jobs:
  deploy:
    environment: production  # uses GitHub Environment protection rules
    steps:
      - name: Deploy
        env:
          DATABASE_URL: ${{ secrets.DATABASE_URL }}
          API_KEY: ${{ secrets.API_KEY }}
          NODE_ENV: production
        run: ./scripts/deploy.sh

Secret management rules:

• Add secrets in: GitHub repo → Settings → Secrets and variables → Actions
• Use GitHub Environments for production secrets (adds approval gates)
• Never print secrets - GitHub redacts known secrets but be careful with transformed values

Pinning third-party actions:

• For untrusted/third-party actions, pin to a full commit SHA rather than a moving tag

(e.g. uses: some/action@<40-char-sha> # v3.1.0). A mutable tag like @v3 can be force-pushed to point at malicious code, so a SHA is the only immutable reference.

• First-party actions/* pinned to a major tag (@v4) is the common, acceptable baseline;

pin to SHAs when your threat model requires strict supply-chain guarantees.

Step 6: Build and Push Docker Image

name: Build and Push Docker Image

on:
  push:
    branches: [main]
    tags: ['v*']

jobs:
  docker:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Log in to GitHub Container Registry
        uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}  # built-in, no setup needed

      - name: Extract metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ghcr.io/${{ github.repository }}
          tags: |
            type=ref,event=branch
            type=semver,pattern={{version}}
            type=sha,prefix=,suffix=,format=short

      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          context: .
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

Step 7: Full CI + CD Pipeline

name: CI/CD

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  # ─── CI: Test and Lint ──────────────────────────────────────────────────────
  ci:
    name: Test and Lint
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npm run lint
      - run: npm run typecheck
      - run: npm test -- --coverage

  # ─── CD: Deploy to Staging ─────────────────────────────────────────────────
  deploy-staging:
    name: Deploy to Staging
    needs: ci
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'
    environment: staging

    steps:
      - uses: actions/checkout@v4
      - name: Deploy to staging
        env:
          DEPLOY_KEY: ${{ secrets.STAGING_DEPLOY_KEY }}
        run: ./scripts/deploy.sh staging

  # ─── CD: Deploy to Production (manual approval required) ───────────────────
  deploy-production:
    name: Deploy to Production
    needs: deploy-staging
    runs-on: ubuntu-latest
    environment: production  # has required reviewers configured
    if: github.ref == 'refs/heads/main'

    steps:
      - uses: actions/checkout@v4
      - name: Deploy to production
        env:
          DEPLOY_KEY: ${{ secrets.PROD_DEPLOY_KEY }}
        run: ./scripts/deploy.sh production

Step 8: Automated Releases

name: Release

on:
  push:
    tags: ['v*']

jobs:
  release:
    runs-on: ubuntu-latest
    permissions:
      contents: write

    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0  # for changelog generation

      - name: Build
        run: npm ci && npm run build

      - name: Create GitHub Release
        uses: softprops/action-gh-release@v2
        with:
          generate_release_notes: true
          files: |
            dist/*.zip
            dist/*.tar.gz

Step 9: Reusable Workflows

# .github/workflows/reusable-test.yml
on:
  workflow_call:
    inputs:
      node-version:
        type: string
        default: '20'
    secrets:
      CODECOV_TOKEN:
        required: true

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: ${{ inputs.node-version }}
      - run: npm ci && npm test

# ─── Call from another workflow ───────────────────────────────────────────────
# .github/workflows/ci.yml
jobs:
  test:
    uses: ./.github/workflows/reusable-test.yml
    with:
      node-version: '20'
    secrets:
      CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

Common Mistakes

• Using `pull_request_target` carelessly - it has write permissions and can expose secrets to PRs from forks; use pull_request for untrusted code
• Pinning actions to `@master` - always pin to a version tag: actions/checkout@v4
• Missing `permissions` - explicitly declare minimum required permissions in the job
• Not using `npm ci` - use npm ci (not npm install) in CI for reproducible installs
• Hardcoding secrets in workflow files - always use ${{ secrets.NAME }}
• No `fail-fast: false` in matrix - by default, one matrix failure cancels all; set fail-fast: false for visibility
• Missing `if: github.ref == 'refs/heads/main'` - deploy jobs must gate on branch
• Not caching dependencies - always set up caching to reduce build times by 50-80%