Github Actions Elixir.yml file that works on my Elixir Phoenix apps using Postgres, such as on Heroku

elixir.yml

name: Elixir CI

on:
  push:
    branches: [ master ]

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        elixir: [1.8.2]
        otp: [22.2]

    services:
      postgres:
        image: postgres
        env:
          POSTGRES_PASSWORD: postgres
        options: >-
          --health-cmd pg_isready
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5
        ports:
          # Maps tcp port 5432 on service container to the host
          - 5432:5432

    steps:
    - uses: actions/checkout@v2
    - name: Setup elixir
      uses: actions/setup-elixir@v1
      with:
        elixir-version: ${{ matrix.elixir }} # Define the elixir version [required]
        otp-version: ${{ matrix.otp }} # Define the OTP version [required]
    - name: Retrieve Mix Dependencies Cache
      uses: actions/cache@v1
      id: mix-cache # id to use in retrieve action
      with:
        path: deps
        key: ${{ runner.os }}-${{ matrix.otp }}-${{ matrix.elixir }}-mix-${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}
    - name: Install Dependencies
      if: steps.mix-cache.outputs.cache-hit != 'true'
      run: |
        mix local.rebar --force
        mix local.hex --force
        mix deps.get
    - name: Run Tests
      run: |
        mix compile
        mix test