Go で HTTP ルート ハンドラーを動的に管理する方法

<code class="go">package main

import (
    "net/http"
    "sync"
)

type HasHandleFunc interface {
    HandleFunc(pattern string, handler func(w http.ResponseWriter, req *http.Request))
}
type Handler struct {
    http.HandlerFunc
    Enabled bool
}
type Handlers map[string]*Handler

func (h Handlers) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    path := r.URL.Path
    if handler, ok := h[path]; ok && handler.Enabled {
        handler.ServeHTTP(w, r)
    } else {
        http.Error(w, "Not Found", http.StatusNotFound)
    }
}

func (h Handlers) HandleFunc(mux HasHandleFunc, pattern string, handler http.HandlerFunc) {
    h[pattern] = &Handler{handler, true}
    mux.HandleFunc(pattern, h.ServeHTTP)
}

func main() {
    mux := http.NewServeMux()
    handlers := Handlers{}
    handlers.HandleFunc(mux, "/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("this will show once"))
        handlers["/"].Enabled = false
        // the route to '/' is now disabled
    })
    http.Handle("/", mux)
    http.ListenAndServe(":9020", nil)
}</code>