build: add codecov upload

Author: manmartgarc

.github/workflows/test.yml

@@ -60,4 +60,9 @@ jobs:
         with:
           go-version: "1.24"
       - name: Test with -race
-        run: go test -v -race ./...
+        run: go test -race -covermode=atomic -coverprofile=coverage.out ./...
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          fail_ci_if_error: true
+          token: ${{ secrets.CODECOV_TOKEN }}