? ? wg := sync.WaitGroup{}
? ? var result1 interface{}
    var result2 interface{}
? ? wg.Add(2)
    go func() {
        defer func() {
            wg.Done()
        }()
        result1 = funcA()
    }()
? ? go func() {
        defer func() {
            wg.Done()
        }()
        result1 = funcB()
    }()  
    wg.wait() 

import (
    "fmt"
    "io/ioutil"
    "net/http"
    "strings"
    "sync"
)
func main() {
    idList := []string{"x", "xx"}
    wg := sync.WaitGroup{}
    dataMap := sync.Map{} //  sync.Map是線程安全的，如果使用 map去存儲(chǔ)返回結(jié)果會(huì)報(bào)錯(cuò)，
                          //  接受返回結(jié)果也可以是channel，channel也是線程安全的
    for _, id := range idList {
        wg.Add(1)
        go func(id string) {
            defer func() {
                wg.Done()
            }()
            data := PostData(id)
            dataMap.Store(id, data)
        }(id)
    }
    wg.Wait()
    for _, id := range idList {
        fmt.Println(dataMap.Load(id))
    }
}
func PostData(id string) string {
    url := "http:xx"
    method := "POST"
    payload := strings.NewReader(fmt.Sprintf(`{"id":"%s"}`, id))
    client := &http.Client{}
    req, err := http.NewRequest(method, url, payload)
    if err != nil {
        fmt.Println(err)
        return ""
    }
    req.Header.Add("Content-Type", "application/json")
    res, err := client.Do(req)
    if err != nil {
        fmt.Println(err)
        return ""
    }
    defer res.Body.Close()
    body, err := ioutil.ReadAll(res.Body)
    if err != nil {
        fmt.Println(err)
        return ""
    }
    return string(body)
}

package main
import (
    "fmt"
    "net/http"
    "sync"
)
func main() {
    urls := []string{"http://a.com", "http://b.com", "http://c.com"}
    // 控制并發(fā)度為2
    concurrency := 2
    sem := make(chan struct{}, concurrency)
    var wg sync.WaitGroup
    for _, url := range urls {
        wg.Add(1)
        go func(url string) {
            sem <- struct{}{} // 獲取信號(hào)量
            defer func() {
                <-sem // 釋放信號(hào)量
                wg.Done()
            }()
            resp, err := http.Get(url)
            if err != nil {
                fmt.Printf("Error fetching %s: %v\n", url, err)
                return
            }
            defer resp.Body.Close()
            fmt.Printf("Fetched %s with status code %d\n", url, resp.StatusCode)
        }(url)
    }
    wg.Wait()
    fmt.Println("All URLs fetched")
}

package main
import (
    "fmt"
    "net/http"
)
func main() {
    urls := []string{"http://www.google.com", "http://www.facebook.com", "http://www.apple.com"}
    // 創(chuàng)建一個(gè)通道來(lái)控制并發(fā)度為2
    concurrency := make(chan struct{}, 2)
    // 創(chuàng)建一個(gè)通道來(lái)接收響應(yīng)結(jié)果
    results := make(chan string, len(urls))
    for _, url := range urls {
        // 啟動(dòng)一個(gè)goroutine來(lái)請(qǐng)求url
        go func(url string) {
            // 從通道中獲取一個(gè)信號(hào)，表示可以開(kāi)始請(qǐng)求
            concurrency <- struct{}{}
            // 發(fā)送http GET請(qǐng)求
            resp, err := http.Get(url)
            if err != nil {
                results <- fmt.Sprintf("%s -> error: %s", url, err)
            } else {
                results <- fmt.Sprintf("%s -> status: %s", url, resp.Status)
                resp.Body.Close()
            }
            // 釋放一個(gè)信號(hào)，表示請(qǐng)求已完成
            <-concurrency
        }(url)
    }
    // 從結(jié)果通道中讀取所有響應(yīng)結(jié)果
    for i := 0; i < len(urls); i++ {
        fmt.Println(<-results)
    }
}

func getData(ctx context.Context, result chan string, id string) {
    for {
        select {
        case <-ctx.Done():
            fmt.Println("running get Data")
            return
        default:
            resultData := PostData(id)
            result <- resultData
        }
    }
}
func main() {
    idList := []string{"xx", "xxx"}
    ctx := context.Background()
    var result = make(chan string, 2)
    go getData(ctx, result, idList[0])
    go getData(ctx, result, idList[1])
    fmt.Println(<-result)
    fmt.Println(<-result)
}
func PostData(id string) string {
    url := "http://xxx"
    method := "POST"
    payload := strings.NewReader(fmt.Sprintf(`{"id":"%s"}`, id))
    client := &http.Client{}
    req, err := http.NewRequest(method, url, payload)
    if err != nil {
        fmt.Println(err)
        return ""
    }
    req.Header.Add("Content-Type", "application/json")
    res, err := client.Do(req)
    if err != nil {
        fmt.Println(err)
        return ""
    }
    defer res.Body.Close()
    body, err := ioutil.ReadAll(res.Body)
    if err != nil {
        fmt.Println(err)
        return ""
    }
    return string(body)
}