Building Scalable REST APIs with Go

Building a REST API that scales well requires more than just setting up routes and handlers. In this article, I'll walk through the patterns and practices I've found most effective when building Go APIs for production.

Project Structure

A well-organized project structure makes it easier to navigate, test, and maintain your codebase. Here's the layout I typically use:

├── cmd/
│   └── server/
│       └── main.go
├── internal/
│   ├── handler/
│   ├── middleware/
│   ├── model/
│   ├── repository/
│   └── service/
├── pkg/
│   └── logger/
├── go.mod
└── go.sum

Middleware Patterns

Middleware in Go is elegantly simple. The standard http.Handler interface makes it natural to chain middleware functions:

func LoggingMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        start := time.Now()
        next.ServeHTTP(w, r)
        log.Printf("%s %s %v", r.Method, r.URL.Path, time.Since(start))
    })
}

Error Handling

Consistent error handling is crucial for a good API. I prefer returning structured error responses:

type APIError struct {
    Code    int    `json:"code"`
    Message string `json:"message"`
}

Key Takeaways

• Keep handlers thin — business logic belongs in services
• Use interfaces — they make testing and dependency injection natural
• Structured logging — use structured logging from day one
• Graceful shutdown — handle signals properly for zero-downtime deployments

Building robust APIs is as much about discipline and patterns as it is about the code itself. The Go standard library gives you excellent building blocks — use them wisely.