Install using cache action and actions/setup-ruby action.

Note, if you use ruby/setup-ruby instead, you get caching already. With the approach here, you get more control over cache and how Bundler runs, if that matters to you.

actions - cache

Based on example.

  • main.yml 
      steps:
    - name: Checkout 🛎️
      uses: actions/checkout@v2

    - name: Set up Ruby 💎
      uses: actions/setup-ruby@v1
      with:
        ruby-version: '2.7'

    - name: Get cached gems
      uses: actions/cache@v2
      with:
        path: vendor/bundle
        key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
        restore-keys: |
          ${{ runner.os }}-gems-

    - name: Install dependencies 🔧
      run: |
        bundle config set path vendor/bundle
        bundle install --jobs 4 --retry 3

    - name: Run
      run: bundle exec ruby hello.rb