Add checkout to workflow

Author: vollborn

.github/workflows/main.yml

@@ -10,6 +10,10 @@ jobs:
     runs-on: self-hosted
     environment: production
     steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          ref: main
       -
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v2