1_no_middleware

Making Middleware Manageable - Part One

To kick things off we've created a simple HTTP server with a single endpoint of /hello. A request to this endpoint returns a friendly greeting.

Usage

To run the application:

go run main.go

To make a request:

curl localhost:8000/hello

Things to Note

HTTP Handlers

The function which handles requests to /hello is defined as:

func helloHandler() http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("Hello Golang Dorset!"))
	})
}

This is a very simple Go function which returns http.Handler. The return type here is an interface provided by the net/http package, it is simply defined as something that response to a HTTP request. The interface has one method: ServeHTTP(ResponseWriter, *Request). See the godoc for more information.

Note that the body of helloHandler actually returns a http.HandlerFunc. This is because http.Handler is just an interface, it cannot do anything by itself. Whereas http.Handlerfunc is an implementation of that interface that allows the returning function to respond to a HTTP request. See the definition of how it is implementation ServeHTTP:

func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
	f(w, r)
}

It simply takes the response (w) and request (r) parameters and runs the original function (f).