[Fix] fix github action

Signed-off-by: Kent Huang <[email protected]>

Author: kentwelcome

.github/workflows/main.yml

@@ -16,7 +16,7 @@ jobs:
         uses: actions/checkout@v2
       - name: Get the version
         id: get_version
-        run: echo ::set-output name=VERSION::$(GITHUB_REF/refs\/tags\//)
+        run: echo ::set-output name=VERSION::${GITHUB_REF/refs\/tags\//}
       - name: Log in to Docker Hub
         uses: docker/login-action@v1
         with: