Work on code coverage report action

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - '**'
+  pull_request:
+    types: [opened, reopened]
+    branches:
+      - '**'
+
+jobs:
+  unit_tests:
+    name: "Unit tests"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: ^1.22
+
+      - name: Test
+        run: go test -v -cover -coverprofile=coverage.txt -covermode=count ./...
+
+      - name: Archive code coverage results
+        uses: actions/upload-artifact@v4
+        with:
+          name: code-coverage
+          path: coverage.txt
+
+  code_coverage:
+    name: "Code coverage report"
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    needs: unit_tests
+    steps:
+      - name: Download code coverage results from source branch
+        run: 'echo "TODO: Download code coverage results from source branch"'
+
+      - name: Download code coverage results
+        uses: actions/download-artifact@v4
+        with:
+          name: code-coverage
+          path: source-coverage.txt
+
+      - name: Compare code coverage results
+        run: 'echo "## Coverage report" > coverage-comment.md'
+
+      - name: Comment on pull request
+        run: gh pr comment ${{ github.event.number }} --body-file coverage-comment.md