Add private repo setup to upgrade_downgrade_test_backups_e2e.yml

Signed-off-by: Tim Vaillancourt <[email protected]>

.github/workflows/upgrade_downgrade_test_backups_e2e.yml

@@ -15,6 +15,9 @@ jobs:
     name: Run Upgrade Downgrade Test - Backups - E2E
     runs-on:
       group: vitess-ubuntu20
+    env:
+      GOPRIVATE: github.com/slackhq/vitess-addons
+      GH_ACCESS_TOKEN: ${{ secrets.GH_ACCESS_TOKEN }}
 
     steps:
     - name: Skip CI
@@ -75,6 +78,9 @@ jobs:
       with:
         go-version: 1.22.3
 
+    - name: Setup github.com/slackhq/vitess-additions access token
+      run: git config --global url.https://[email protected]/.insteadOf https://github.com/
+
     - name: Set up python
       if: steps.skip-workflow.outputs.skip-workflow == 'false' && steps.changes.outputs.end_to_end == 'true'
       uses: actions/setup-python@v5