cache docker layers in release-slackbot-proxy.yml workflow

.github/workflows/release-slackbot-proxy.yml

@@ -54,6 +54,14 @@ jobs:
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v1
 
+    - name: Cache Docker layers
+      uses: actions/cache@v2
+      with:
+        path: /tmp/.buildx-cache
+        key: ${{ runner.os }}-buildx-slackbot-proxy-${{ github.sha }}
+        restore-keys: |
+          ${{ runner.os }}-buildx-slackbot-proxy-
+
     - name: Build and push
       uses: docker/build-push-action@v2
       with:
@@ -61,8 +69,14 @@ jobs:
         file: ./packages/slackbot-proxy/docker/Dockerfile
         platforms: linux/amd64
         push: true
+        cache-from: type=local,src=/tmp/.buildx-cache
+        cache-to: type=local,mode=max,dest=/tmp/.buildx-cache-new
         tags: ${{ steps.meta.outputs.tags }}
 
+    - name: Move cache
+      run: |
+        rm -rf /tmp/.buildx-cache
+        mv /tmp/.buildx-cache-new /tmp/.buildx-cache
 
     - name: Update Docker Hub Description
       uses: peter-evans/dockerhub-description@v2