HTTP Middleware

What is middleware?

Middleware wraps an http.Handler to add cross-cutting behaviour — logging, authentication, rate-limiting, CORS — without polluting route handlers.

The signature every Go middleware follows:

http.HandlerFunc is a function type that implements http.Handler — it lets you turn any compatible function into a handler.

Logging middleware

Auth middleware

Short-circuiting (returning before calling next.ServeHTTP) is how middleware rejects requests.

Chaining middleware

Apply multiple middlewares by nesting them:

Or write a Chain helper:

Middlewares are applied right-to-left so that the leftmost runs first on incoming requests.

Capturing the response status

To log the status code, wrap ResponseWriter in a recorder:

Then in the middleware:

Passing values through context

Middleware can attach request-scoped values for downstream handlers:

http.StripPrefix and http.TimeoutHandler

Standard library provides ready-made middleware: