Go thing

gistfile1.go

package main

import "net/http"
import "fmt"

func hello(w http.ResponseWriter, r *http.Request) {
	contentType := w.Header().Get("Content-Type")
	if contentType == "application/json" {
		fmt.Fprintln(w, `{"Hello": "JSON"}`)
	} else {
		w.Header().Set("Content-Type", "text/plain")
		fmt.Fprintln(w, "Hello wrapped world")
	}
}

func wrapMiddleware(f http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("X-Wrapped", "true")
		contentType := r.Header.Get("Content-Type")
		if contentType != "" {
			w.Header().Set("Content-Type", contentType)
		}
		f(w, r)
	}
}

func main() {
	handler := wrapMiddleware(hello)
	http.HandleFunc("/", handler)
	http.ListenAndServe(":5000", nil)
}