Add ref to checkout action

Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>

Author: glours

.github/workflows/release-weekly-build.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Checkout code into the Go module directory
         uses: actions/checkout@v2
         with:
-          ${{ github.event.inputs.branch }}
+          ref: ${{ github.event.inputs.branch }}
 
       - name: Golang cache
         uses: actions/cache@v1