action only in master branch

.github/workflows/docker.yml

@@ -1,9 +1,8 @@
 name: Publish Docker image
-#on:
-#  release:
-#    types: [published]
 
-on: push
+on: 
+  push:
+    - master
 
 jobs:
   publish:
@@ -25,8 +24,6 @@ jobs:
           TAGS="${TAGS},${IMAGE}:latest"
         fi
         echo ::set-output name=tags::${TAGS}
-    #- name: Docker Buildx setup
-    #  uses: docker/setup-buildx-action@v1
     - name: Login in to registry
       uses: docker/login-action@v1
       with: