fix github actions setting

```
issue detecting commit SHA. Please run actions/checkout with fetch-depth > 1 or set to 0
```

Reference: codecov/codecov-action#190

Author: Praveenrajmani

.github/workflows/go.yml

@@ -27,6 +27,8 @@ jobs:
 
       - name: Check out code into the Go module directory
         uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
 
       - name: Build and upload coverage to Codecov
         env: