ci: add codecov action

.github/workflows/codecov.yml

@@ -0,0 +1,36 @@
+name: Codecov
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.18'
+      id: go
+
+    - name: Check out code into the Go module directory
+      uses: actions/checkout@v3
+
+    - name: Get dependencies
+      run: go get -v -t -d ./...
+
+    - name: Coverage
+      run: go test -v -cover -race -coverprofile=coverage -covermode=atomic
+
+    - name: Upload coverage
+      if: github.event_name == 'push'
+      uses: codecov/codecov-action@v3
+      with:
+        file: ./coverage
+        verbose: true