title: How do I install private packages using yarn inside a Github Action?
body: <p>My current workflow:</p>
  
  <pre><code>name: Node CI
  
  on: [push]
  
  jobs:
    build:
      runs-on: ubuntu-latest
  
      strategy:
        matrix:
          node-version: [10.x]
  
      steps:
        - uses: actions/checkout@v1
        - name: Use Node.js ${{ matrix.node-version }}
          uses: actions/setup-node@v1
          with:
            node-version: ${{ matrix.node-version }}
        - name: npm install, build, and test
          run: |
            npm install yarn -g
            yarn
            yarn test
          env:
            CI: true
            NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
  </code></pre>
  
  <p>I have setup my <code>NPM_TOKEN</code> in the repo secrets area.</p>
  
  <p>The token is also in use on Netlify, and the netlify build process works.</p>
  
  <p>When this workflow runs, I get a 404 for any of my private packages.</p>
  
  <p>What am I doing wrong?</p>