How to change the Context to other dir?

The default context is . ,it’s the root dir,but if my Dockerfile is in ./alpine/Dockerfile,and my root dir include multiple Dockerfile,I get the docker image by git msg.

[CremaLuca]

Solved: adding

- name: Checkout
  uses: actions/checkout@v2

At the beginning of the Github actions file

[CremaLuca]

Solved: adding

- name: Checkout
  uses: actions/checkout@v2

At the beginning of the Github actions file

Can you share your file ,I add the check out ,it is also did not work

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - 
        name: Checkout
        uses: actions/checkout@v2
        with:
          fetch-depth: 0
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v1
      -
        uses: docker/setup-buildx-action@v1
        id: builder1
      -
        uses: docker/setup-buildx-action@v1
        id: builder2
      -
        name: Login to DockerHub
        uses: docker/login-action@v1 
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push 1
        id: docker_build1
        uses: docker/build-push-action@v2
        with:
          builder: ${{ steps.builder1.outputs.name }}
          context: ./app
          file: ./app/Dockerfile
          push: true
          tags: user/name-app:latest
      -
        name: Build and push 2
        id: docker_build2
        uses: docker/build-push-action@v2
        with:
          builder: ${{ steps.builder2.outputs.name }}
          context: ./web
          file: ./web/Dockerfile
          push: true
          tags: user/name-web:latest