Using Github action cache

I am using github actions to run tests for my Elixir repo. Here is part of my github workflow .yml:

    steps:
      - uses: actions/checkout@v2
      - uses: erlef/setup-elixir@v1
        with:
          otp-version: '23.1.2'
          elixir-version: '1.11.2'

      - name: Restore dependencies cache
        uses: actions/cache@v2
        with:
          path: deps
          key: ${{ runner.os }}-mix-${{ hashFiles('mix.lock') }}-myapp
          restore-keys: ${{ runner.os }}-mix-myapp-

      - name: Restore build cache
        uses: actions/cache@v2
        with:
          path: _build
          key: ${{ runner.os }}-build-${{ hashFiles('mix.lock') }}-myapp
          restore-keys: ${{ runner.os }}-build-myapp

      - name: Get deps
        run: |
          mix local.hex --force
          mix local.rebar
          mix deps.get

      - name: Compile
        run: mix compile

      - name: Test
        run: mix test

I followed cache/examples.md at main · actions/cache · GitHub but still my compile time is very slow when I do PRs. Did I do somethings wrong? Maybe I need more options for restore-keys? Compile time sometimes is 3 minutes. Thank you for ideas!