ci: implement coveralls

.github/workflows/coverage.yml

@@ -0,0 +1,26 @@
+name: Tests
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.19
+
+      - name: Unit tests
+        run: go test -v -coverprofile=cover.out -bench=. ./...
+
+      - name: Send coverage
+        uses: shogo82148/actions-goveralls@v1
+        with:
+          path-to-profile: cover.out