ci(actions): checkout code for release job

.github/workflows/main.yml

@@ -55,6 +55,8 @@ jobs:
     runs-on: ubuntu-latest
     needs: build
     steps:
+      - name: Check out code into the Go module directory
+        uses: actions/checkout@v1
       - uses: actions/download-artifact@v1
         with:
           name: build