2_first_middleware

Making Middleware Manageable - Part Two

Ok so for part two we've realised that we need to secure the /hello endpoint of our application. We'll do this with an API key.

Usage

To run the application:

go run main.go

To make a request:

curl localhost:8000/hello

This will fail because you have no api key.

To make an authenticated request:

curl -H "x-api-key: foo-bar-baz" localhost:8000/hello

Things to Note

Middleware

We defined our first middleware, to check API keys, as follows:

func checkAPIKey(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get(apiKeyHeader) != apiKey {
			w.WriteHeader(http.StatusUnauthorized)
			w.Write([]byte("Unauthorised"))
			return
		}

		h.ServeHTTP(w, r)
	})
}

You'll notice that the signature for the function is very similar to that of helloHandler in that it returns a http.Handler interface. The key difference here is that we're also taking in a http.Handler interface as a parameter.

This parameter is the original handler function, it is in effect being wrapped by the middleware. In this case we check the API key header and then run the original handler function by calling h.ServeHTTP(w, r)