在Go语言中如何解决并发网络请求的请求限速和流量控制问题？

package main

import (
    "fmt"
    "sync"
    "time"
)

func request(url string, token chan struct{}, wg *sync.WaitGroup) {
    defer wg.Done()
    
    // 发送一个token表示开始请求
    token <- struct{}{}
    
    // 模拟请求耗时
    time.Sleep(1 * time.Second)
    
    // 完成请求后接收一个token
    <-token
    
    fmt.Println("Request completed:", url)
}

func main() {
    urls := []string{"http://example.com", "http://example.org", "http://example.net"}
    maxConcurrentRequests := 2
    token := make(chan struct{}, maxConcurrentRequests)
    var wg sync.WaitGroup
    
    for _, url := range urls {
        wg.Add(1)
        go request(url, token, &wg)
    }
    
    wg.Wait()
}

package main

import (
    "fmt"
    "io/ioutil"
    "net/http"
    "time"
)

func sendRequest(url string) {
    resp, err := http.Get(url)
    if err != nil {
        fmt.Println("Failed to send request:", err)
        return
    }
    defer resp.Body.Close()
    
    // 读取响应数据
    data, _ := ioutil.ReadAll(resp.Body)
    fmt.Println("Response:", string(data))
}

func main() {
    urls := []string{"http://example.com", "http://example.org", "http://example.net"}
    rate := time.Second / 2 // 控制请求速率为每秒2次
    ticker := time.NewTicker(rate)

    for {
        select {
        case <-ticker.C:
            for _, url := range urls {
                go sendRequest(url)
            }
        }
    }
}