Build arm64 container images (#1855)

* Build container image on aarch64 platform

* Revert test code & correct typo

Co-authored-by: erin <erin@localhost>

.github/workflows/docker-image.yml

     tags:
       - 'v*'
 
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
 jobs:
   build:
-    name: 'Build'
+    name: Build
     runs-on: ubuntu-latest
     steps:
-      - name: "Build:checkout"
+      - name: Checkout Git repository
         uses: actions/checkout@v2
-      - name: "Build:meta"
-        id: meta
-        uses: docker/metadata-action@v3
-        with:
-          images: ghcr.io/ergochat/ergo           
-      - name: "Build:login"
+
+      - name: Authenticate to container registry
         uses: docker/login-action@v1
         if: github.event_name != 'pull_request'
         with:
-          registry: ghcr.io
+          registry: ${{ env.REGISTRY }}
           username: ${{ github.repository_owner }}
           password: ${{ secrets.GITHUB_TOKEN }}
-      - name: 'Build:dockerimage'
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
+      - name: Setup Docker buildx driver
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Build and publish image
         uses: docker/build-push-action@v2
         with:
           context: .
           push: ${{ github.event_name != 'pull_request' }}
+          platforms: linux/amd64,linux/arm64
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}