fixed bug in ci.yml

* login to dockerhub

.github/workflows/ci.yml

@@ -27,6 +27,11 @@ jobs:
       - uses: actions/checkout@master
         with:
           ref: ${{ github.ref }}
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
       - name: Build
         env:
           VERSION: ${{ github.run_number }}