实现HTTP处理器的中间件

package main

import "net/http"
import "fmt"

func hello(w http.ResponseWriter, r *http.Request) {
    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")
        f(w, r)
    }
}

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

运行结果：

$ go run middleware.go

$ curl -i http://127.0.0.1:5000/
HTTP/1.1 200 OK
Content-Type: text/plain
Date: Tue, 02 Oct 2012 00:37:18 GMT
Transfer-Encoding: chunked
X-Wrapped: true

Hello wrapped world