ci(codecov) Add code coverage

.github/workflows/coverage.yml

@@ -0,0 +1,22 @@
+name: "coverage"
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    name: Send coverage to codecov
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Go
+        uses: actions/setup-go@v1
+        with:
+          go-version: "1.14"
+      - run: go mod download
+      - run: go test -race -coverprofile=coverage.txt -covermode=atomic
+      - uses: codecov/codecov-action@v1
+        with:
+          file: ./coverage.txt

README.md

@@ -5,6 +5,7 @@
 [![go.dev reference](https://img.shields.io/badge/go.dev-reference-007d9c)](https://pkg.go.dev/github.com/stanleynguyen/is-thirteen)
 ![](https://github.com/stanleynguyen/is-thirteen/workflows/test/badge.svg)
 ![](https://github.com/stanleynguyen/is-thirteen/workflows/lint/badge.svg)
+[![codecov](https://codecov.io/gh/stanleynguyen/is-thirteen/branch/master/graph/badge.svg)](https://codecov.io/gh/stanleynguyen/is-thirteen)
 
 Check if a number is equal to 13. A port of [this NPM module](https://github.com/jezen/is-thirteen).