Fix docker image metadata (#14)

.github/workflows/autorelease.yml

@@ -5,6 +5,10 @@ on:
     types: [closed]
     branches:
       - master
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{github.repository}}
+
 jobs:
   github-release:
     if: github.event.pull_request.merged == true && contains(toJSON(github.event.pull_request.labels.*.name), '"autorelease"')
@@ -53,9 +57,6 @@ jobs:
   build-and-push-docker-image:
     needs: github-release
     runs-on: ubuntu-latest
-    env:
-      REGISTRY: ghcr.io
-      IMAGE_NAME: ${{github.repository}}
     permissions:
       contents: read
       packages: write
@@ -64,6 +65,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v2
 
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
       - name: Log in to the Container registry
         uses: docker/[email protected]
         with:
@@ -75,7 +80,7 @@ jobs:
         id: meta
         uses: docker/[email protected]
         with:
-          images: ${{ env.IMAGE_NAME }},ghcr.io/${{ env.IMAGE_NAME }}
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
             type=semver,pattern={{version}},value=${{needs.github-release.outputs.version }}