Update ci.yml

first move to buildx for multiarch build

.github/workflows/ci.yml

@@ -45,6 +45,16 @@ jobs:
         env:
           COVERALLS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx  
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+        
+      - name: Available platforms
+        run: echo ${{ steps.buildx.outputs.platforms }}
+
       - name: build and deploy image
         if: ${{ github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/tags/') }}
         env:
@@ -54,5 +64,6 @@ jobs:
           ref="$(echo ${GITHUB_REF} | cut -d'/' -f3)"
           echo GITHUB_REF - $ref
           echo ${GITHUB_PACKAGE_TOKEN} | docker login ghcr.io -u ${USERNAME} --password-stdin
-          docker build -t ghcr.io/${USERNAME}/reproxy:${ref} .
-          docker push ghcr.io/${USERNAME}/reproxy:${ref}
+          docker buildx build --push \
+              --platform linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64 \
+              -t ghcr.io/${USERNAME}/reproxy:${ref} .