Add test coverage reporting and Codecov badge

.github/workflows/coverage.yaml

@@ -0,0 +1,40 @@
+name: Go
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+      branches: [master]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    services:
+        redis:
+          image: redis/redis-stack-server:edge
+          options: >-
+            --health-cmd "redis-cli ping" --health-interval 10s --health-timeout 5s --health-retries 5
+          ports:
+            - 6379:6379
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.21
+
+    - name: Install dependencies
+      run: go mod tidy
+
+    - name: Run tests
+      run: go test -coverprofile=coverage.out ./...
+
+    - name: Upload to Codecov
+      uses: codecov/codecov-action@v4
+      with:
+        files: coverage.out
+        token: ${{ secrets.CODECOV_TOKEN }}

README.md

@@ -3,6 +3,7 @@
 [![build workflow](https://github.com/redis/go-redis/actions/workflows/build.yml/badge.svg)](https://github.com/redis/go-redis/actions)
 [![PkgGoDev](https://pkg.go.dev/badge/github.com/redis/go-redis/v9)](https://pkg.go.dev/github.com/redis/go-redis/v9?tab=doc)
 [![Documentation](https://img.shields.io/badge/redis-documentation-informational)](https://redis.uptrace.dev/)
+[![codecov](https://codecov.io/github/redis/go-redis/graph/badge.svg?token=tsrCZKuSSw)](https://codecov.io/github/redis/go-redis)
 [![Chat](https://discordapp.com/api/guilds/752070105847955518/widget.png)](https://discord.gg/rWtp5Aj)
 
 > go-redis is brought to you by :star: [**uptrace/uptrace**](https://github.com/uptrace/uptrace).