specify submodules: true

.github/workflows/docker-build-push-dockerhub.yml

@@ -22,6 +22,8 @@ jobs:
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
+        with:
+          submodules: true
 
       - name: Docker Login
       # You may pin to the exact commit or the version.