add codecov support

.github/workflows/codecov.yml

@@ -0,0 +1,18 @@
+name: Test and coverage
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run coverage
+        run: go test ./... -race -coverprofile=coverage.out -covermode=atomic
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: false
+          files: ./coverage.out
+          move_coverage_to_trash: true