Go Web Service Template

Create a Go web service template for:

Service Name: {{SERVICE_NAME}}
Router: {{ROUTER}} (Chi/Gin/Echo/stdlib)
Database: {{DATABASE}}
Features: {{FEATURES}}

Generate complete Go structure:

1. **Project Layout:**
   - cmd/api/main.go
   - internal/handlers/
   - internal/models/
   - internal/repository/
   - internal/middleware/
   - pkg/

2. **Main Entry (main.go):**
   - Configuration loading
   - Database connection
   - Router setup
   - Graceful shutdown
   - Signal handling

3. **Handlers:**
   - Handler interface
   - HTTP handler functions
   - Request parsing
   - Response writing
   - Error handling

4. **Middleware:**
   - Logging middleware
   - Authentication middleware
   - CORS middleware
   - Rate limiting
   - Request ID

5. **Models:**
   - Struct definitions
   - Validation tags
   - JSON serialization
   - Database tags

6. **Repository Pattern:**
   - Interface definitions
   - Database implementations
   - Mock implementations
   - Transaction handling

7. **Configuration:**
   - Viper/envconfig setup
   - Environment variables
   - Config struct
   - Validation

8. **Testing:**
   - Handler tests
   - Repository tests
   - Integration tests
   - Testcontainers setup

9. **Build and Deploy:**
   - Makefile
   - Dockerfile (multi-stage)
   - Docker Compose

Include health check and metrics endpoints.