rearrange workflow

.github/workflows/build.yml

@@ -60,4 +60,9 @@ jobs:
           DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
           DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
         if: github.event_name == 'push'
-        run: bash hack/docker_build.sh ${{ steps.extract_branch.outputs.branch }}
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+        run: bash hack/docker_build.sh ${{ steps.extract_branch.outputs.branch }}
+
+      - name: Slack notify
+        uses: rtCamp/action-slack-notify@v2.0.0
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}
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