Do Flutter unit test and lint in GitHub Actions

unit_test_and_lint.yml

name: Unit test and lint
on: [push, pull_request]
jobs:
  lint-and-test:
    name: Test on ${{ matrix.os }}
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest, windows-latest, macOS-latest]
    steps:
      - uses: actions/checkout@v1
      - uses: actions/setup-java@v1
        with:
          java-version: '12.x'
      - uses: subosito/flutter-action@v1
        with:
          flutter-version: '1.9.1+hotfix.2'
          channel: 'stable'
      - name: Upgrade flutter
        run: |
          flutter channel master
          flutter upgrade
      - name: Install packages
        run: |
          cd ./rock_paper_scissors
          flutter pub get
      - name: Lint
        run: |
          cd ./rock_paper_scissors
          flutter analyze
      - name: Unit test
        run: |
          cd ./rock_paper_scissors
          flutter test