How to run cached Docker image in Github Action?

Question

I don't know how to run a cached Docker image in Github Actions.
I've followed a tutorial about Publishing Docker images to implement a task that would cache, build and push Docker image to a DockerHub.
I need to build, cache and run the image, the image publishing is optional.
My goal is to speed up CI workflow.
Here is the Github Actions workflow:

name: CI

# Controls when the action will run. 
on:
  # Triggers the workflow on push or pull request events but only for the master branch
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:

# A workflow run is made up of one or more jobs that can run sequentially or in parallel
jobs:
  # This workflow contains a single job called "build"
  build:
    # The type of runner that the job will run on
    runs-on: ubuntu-latest

    # Steps represent a sequence of tasks that will be executed as part of the job
    steps:
      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
      - name: Check Out Repo
        uses: actions/checkout@v2
        with:
          fetch-depth: 0

      - name: Set up Docker Buildx
        id: buildx
        uses: docker/setup-buildx-action@v1 

      - name: Cache Docker layers
        uses: actions/cache@v2
        with:
          path: /tmp/.buildx-cache
          key: ${{ runner.os }}-buildx-${{ github.sha }}
          restore-keys: |
            ${{ runner.os }}-buildx-

      - name: Login to Docker Hub
        uses: docker/login-action@v1
        with: 
          username: ${{ secrets.DOCKER_HUB_USERNAME }}
          password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}

      - name: Build and push
        id: docker_build
        uses: docker/build-push-action@v2
        with:
          context: ./
          file: ./Dockerfile
          builder: ${{ steps.buildx.outputs.name }}
          push: true
          tags: ivan123123/c_matrix_library:latest
          cache-from: type=local,src=/tmp/.buildx-cache
          cache-to: type=local,dest=/tmp/.buildx-cache

      #- name: Run Docker container
      #  run: ???

      # Upload gcovr code coverage report
      - name: Upload GCC Code Coverage Report
        uses: actions/upload-artifact@v2
        with:
          name: coveragereport
          path: ./builddir/meson-logs/coveragereport/
        
      - name: Upload code coverage reports to codecov.io page
        run: bash <(curl -s https://codecov.io/bash) 

Edit:
I've found no solution to running cached Docker image, but I have managed to build cached image every time I run CI workflow with docker/setup-buildx-action@v1 action. Because the image is cached, we don't need to download every Docker image dependencies thus saving time from 3 minutes originally to only 40 seconds. Below is the Github Actions workflow:

name: CI

on: [push, pull_request]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Check Out Repo
        uses: actions/checkout@v2
        with:
          fetch-depth: 0

      - name: Set up Docker Buildx
        id: buildx
        uses: docker/setup-buildx-action@v1 

      - name: Cache register
        uses: actions/cache@v2
        with:
          path: /tmp/.buildx-cache
          key: ${{ runner.os }}-buildx-${{ hashFiles('**/Dockerfile') }}

      - name: Build Docker image
        uses: docker/build-push-action@v2
        with:
          context: ./
          file: ./Dockerfile
          builder: ${{ steps.buildx.outputs.name }}
          load: true
          tags: c_matrix_library:latest
          cache-from: type=local,src=/tmp/.buildx-cache
          cache-to: type=local,dest=/tmp/.buildx-cache

      - name: Run Docker container
        run: docker run -v "$(pwd):/app" c_matrix_library:latest

Answer 1

Edit:

As mentioned by Romain in the comments. The initial solution will pull the image at the beginning of the workflow and as such will not use the image that is built during the workflow. The only solution seem to be running docker run yourself in the step:

- name: Run my docker image
  run: >
    docker run -t ivan123123/c_matrix_library:latest
    ...

On a side note. Using this solution might get a bit complicated if you use services in your job. In which case, the networking between your container and the service containers will be troublesome

Original answer:

To run the image you can use the following:

- name: Run my docker image
  uses: docker://ivan123123/c_matrix_library:latest
  with:
    entrypoint: ...
    args: ...

The entrypoint and args are optional. You can find more info here. One limitation though is that you can use any variable or context in the uses field. You can only hardcode the name and tag of the image.