Golang 函数并发编程如何进行限流和负载均衡？

package main

import (
    "context"
    "fmt"
    "log"
    "net/http"
    "time"

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

func main() {
    // 每秒允许 100 个请求
    limiter := rate.NewLimiter(rate.Limit(100), 100)

    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        ctx := context.Background()

        // 从限流器获取令牌
        if err := limiter.Wait(ctx); err != nil {
            http.Error(w, "Too many requests", http.StatusTooManyRequests)
            return
        }

        fmt.Fprintf(w, "Hello, World!")
    })

    log.Fatal(http.ListenAndServe(":8080", nil))
}

package main

import (
    "log"
    "net/http"
    "net/http/httputil"
    "net/url"
)

func main() {
    // 目标服务器的 URL 列表
    targets := []string{
        "http://localhost:8081",
        "http://localhost:8082",
    }

    // 创建反向代理 Director
    director := func(req *http.Request) {
        // 轮询选择目标服务器
        target := targets[len(targets)%len(targets)]

        // 设置请求的远端地址
        req.URL.Host = target
        req.URL.Scheme = "http"
    }

    // 创建反向代理
    proxy := httputil.NewSingleHostReverseProxy(&url.URL{Scheme: "http", Host: "localhost:8080"})
    proxy.Director = director

    log.Fatal(http.ListenAndServe(":8080", proxy))
}