Upgrade codecov action to v5 and add token

Author: MimoJanra

.github/workflows/test.yml

@@ -36,8 +36,9 @@ jobs:
           fi
 
       - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v4
+        uses: codecov/codecov-action@v5
         with:
+          token: ${{ secrets.CODECOV_TOKEN }}
           files: ./coverage.out
           flags: unittests
           name: codecov-${{ matrix.go-version }}