package mainimport ( ???"io" ???"log" ???"net/http")type User stringfunc (u User) toString() string { ???return string(u)}type AuthHandler func(u User, w http.ResponseWriter, r *http.Request)func main() { ???// Secured API ???mux := http.NewServeMux() ???mux.HandleFunc("/api/users", Secure(func(w http.ResponseWriter, r *http.Request) { ???????io.WriteString(w, `[{"id":"1","login":"ffghi"},{"id":"2","login":"ffghj"}]`) ???})) ???mux.HandleFunc("/api/profile", WithUser(func(u User, w http.ResponseWriter, r *http.Request) { ???????log.Println(u.toString()) ???????io.WriteString(w, "{\"user\":\""+u.toString()+"\"}") ???})) ???http.ListenAndServe(":8080", mux)}func WithUser(h AuthHandler) http.HandlerFunc { ???return func(w http.ResponseWriter, r *http.Request) { ???????user := r.Header.Get("X-User") ???????if len(user) == 0 { ???????????w.WriteHeader(http.StatusUnauthorized) ???????????return ???????} ???????h(User(user), w, r) ???}}func Secure(h http.HandlerFunc) http.HandlerFunc { ???return func(w http.ResponseWriter, r *http.Request) { ???????sec := r.Header.Get("X-Auth") ???????if sec != "authenticated" { ???????????w.WriteHeader(http.StatusUnauthorized) ???????????return ???????} ???????h(w, r) // use the handler ???}}/*(sx3.5.3) ? ?~ curl -X GET -I http://127.0.0.1:8080/api/usersHTTP/1.1 401 UnauthorizedDate: Mon, 26 Mar 2018 15:42:50 GMTContent-Length: 0Content-Type: text/plain; charset=utf-8curl -X GET -w "\nStatus: %{http_code}\n" ?http://127.0.0.1:8080/api/usersStatus: 401curl -X GET -w "\nStatus: %{http_code}\n" ?http://127.0.0.1:8080/api/users ?-H "X-Auth: authenticated"[{"id":"1","login":"ffghi"},{"id":"2","login":"ffghj"}]Status: 200(sx3.5.3) ? ?~ curl -X GET -w "\nStatus: %{http_code}\n" ?http://127.0.0.1:8080/api/profile ?-H "X-User: zrd"{"user":"zrd"}Status: 200*/
在前面的例子中中间件的实现利用函数为一等公民的Golang特色。原handlerfunc包装成一个handlerfunc检查x-auth头。安全功能是用来保护handlerfunc，用于servemux的handlefunc方法。请注意，这只是一个简单的示例，但这种方式可以实现更复杂的解决方案。例如，用户的身份可以从标题标记和随后的提取，处理新类型可以定义为类AuthHandler func（U *用户，W http.responsewriter，R * HTTP请求）。功能的用户创建的servemux的handlerfunc。