Add Slack notification

.github/workflows/close-milestone-on-release.yml

@@ -22,14 +22,24 @@ jobs:
     steps:
 
       - name: Close Milestone
+        id: milestone-id
         run: |
           TAG=${{ inputs.releaseTag }}
           export MILESTONE_NAME=${TAG#v}
           MILESTONE_ID=$(gh api repos/$OWNER/$REPO/milestones --jq '.[] | select(.title == env.MILESTONE_NAME) | .number')
-          gh api -X PATCH repos/$OWNER/$REPO/milestones/$MILESTONE_ID -f state='closed' --silent
+          if [ $MILESTONE_ID ]; then
+            gh api -X PATCH repos/$OWNER/$REPO/milestones/$MILESTONE_ID -f state='closed' --silent
+          fi
+          echo version=$MILESTONE_NAME >> $GITHUB_OUTPUT
         env:
           GITHUB_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}
           OWNER: ${{ github.repository_owner }}
           REPO: ${{ github.event.repository.name }}
 
-
+      - name: Announce Release on Slack
+        uses: slackapi/slack-github-action@v1.24.0
+        env:
+          SLACK_WEBHOOK_URL: ${{ secrets.SPRING_RELEASE_SLACK_WEBHOOK_URL }}
+          SLACK_WEBHOOK_TYPE: INCOMING_WEBHOOK
+        with:
+          slack-message: ${{ github.event.repository.name }}-announcing `${{ steps.milestone-id.outputs.version }}`