add dockerhub login step

.github/workflows/release.yml

@@ -70,6 +70,11 @@ jobs:
         uses: actions/setup-go@v2
         with:
           go-version: 1.15.x
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
       - name: Build
         uses: goreleaser/goreleaser-action@v2
         with:
@@ -140,7 +145,6 @@ jobs:
             --variant v8
       - name: Push manifests to Dockerhub
         run: |
-          echo "$DOCKER_PASS" | docker login -u $DOCKER_USER --password-stdin && \
             docker manifest push containrrr/watchtower:$(echo $TAG | sed 's/^v*//') && \
             docker manifest push containrrr/watchtower:latest