如何限制http.HandleFunc并发数量？

楼主的那个效果只能改源码

package main

import (
    "fmt"
    "net/http"
    "net/http/httptest"
    "time"

    "golang.org/x/time/rate"
)

type LimiterOption struct {
    lm *rate.Limiter
}

func WithLimiter(duration time.Duration, count int) func(o *LimiterOption) {
    return func(o *LimiterOption) {
        o.lm = rate.NewLimiter(rate.Every(duration), count)
    }
}

// LimiterWrap 每个 handler 单独限制
func LimiterWrap(f http.HandlerFunc, opts ...func(o *LimiterOption)) http.HandlerFunc {
    o := &LimiterOption{
        lm: rate.NewLimiter(rate.Every(100*time.Millisecond), 10),
    }
    for _, opt := range opts {
        opt(o)
    }

    return func(w http.ResponseWriter, r *http.Request) {
        if !o.lm.Allow() {
            w.WriteHeader(http.StatusInternalServerError)
            return
        }
        f(w, r)
    }
}

func xHandle(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Hello\n"))
}

func main() {
    // 单独控制一个接口
    http.HandleFunc("/", LimiterWrap(xHandle, WithLimiter(100*time.Millisecond, 1)))

    // 所有接口都走同一个限流
    // http.ListenAndServe(":8080", LimiterWrap(http.DefaultServeMux.ServeHTTP))

    for i := 0; i < 10; i++ {
        w := httptest.NewRecorder()
        req, _ := http.NewRequest(http.MethodGet, "/", nil)
        http.DefaultServeMux.ServeHTTP(w, req)
        fmt.Println(i, w.Code)
        time.Sleep(time.Millisecond * 20)
    }
    //output
    //0 200
    //1 500
    //2 500
    //3 500
    //4 500
    //5 200
    //6 500
    //7 500
    //8 500
    //9 500
}

package main

func success() {}

func fail() {}

func main() {
    c := make(chan struct{}, 16)

    select {
    case c <- struct{}{}:
        success()
        <-c
    default:
        fail()
    }
}