Codecov integration: generate and print

Author: horothesun

.github/workflows/ci-linux.yml

@@ -18,6 +18,9 @@ jobs:
       with:
         access_token: ${{ github.token }}
 
+    - name: Intall llvm-cov
+      run: apt-get install llvm-9
+
     - uses: actions/checkout@v2
     - name: Build
       run: swift build -v