feat: start measuring code coverage (#23)

Adapted from rbmk-project/x#69.

.github/workflows/go.yml

@@ -10,7 +10,7 @@ on:
     branches: ["main"]
 
 jobs:
-  build:
+  build_and_test:
     strategy:
       matrix:
         goversion:
@@ -32,4 +32,25 @@ jobs:
         run: go build ./...
 
       - name: Test
-        run: go test -race -cover ./...
+        run: go test -race ./...
+
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          # Here we should use the current go version
+          go-version: "1.24"
+
+      - name: Measure Coverage
+        run: go test -short -race -covermode=atomic -coverprofile=coverage.out ./...
+
+      - name: Upload Coverage
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          file: ./coverage.out
+          fail_ci_if_error: true

README.md

@@ -1,6 +1,6 @@
 # dnscore - DNS Measurement Library
 
-[![GoDoc](https://pkg.go.dev/badge/github.com/rbmk-project/dnscore)](https://pkg.go.dev/github.com/rbmk-project/dnscore)
+[![GoDoc](https://pkg.go.dev/badge/github.com/rbmk-project/dnscore)](https://pkg.go.dev/github.com/rbmk-project/dnscore) [![Build Status](https://github.com/rbmk-project/dnscore/actions/workflows/go.yml/badge.svg)](https://github.com/rbmk-project/dnscore/actions) [![codecov](https://codecov.io/gh/rbmk-project/dnscore/branch/main/graph/badge.svg)](https://codecov.io/gh/rbmk-project/dnscore)
 
 `dnscore` is a Go library designed for performing DNS measurements.  Its high-level
 API, `*dnscore.Resolver`, is compatible with `*net.Resolver`. Its low-level API,