golang 使用goroutine

Posted 2021-05-24

// 等待所有 goroutine 执行完毕
// 使用传址方式为 WaitGroup 变量传参
// 使用 channel 关闭 goroutine

func main() {
    var wg sync.WaitGroup
    done := make(chan struct{})
    ch := make(chan interface{})

    workerCount := 2
    for i := 0; i < workerCount; i++ {
        wg.Add(1)
        go doIt(i, ch, done, &wg)    // wg 传指针，doIt() 内部会改变 wg 的值
    }

    for i := 0; i < workerCount; i++ {    // 向 ch 中发送数据，关闭 goroutine
        ch <- i
    }

    close(done)
    wg.Wait()
    close(ch)
    fmt.Println("all done!")
}

func doIt(workerID int, ch <-chan interface{}, done <-chan struct{}, wg *sync.WaitGroup) {
    fmt.Printf("[%v] is running\n", workerID)
    defer wg.Done()
    for {
        select {
        case m := <-ch:
            fmt.Printf("[%v] m => %v\n", workerID, m)
        case <-done:
            fmt.Printf("[%v] is done\n", workerID)
            return
        }
    }
}

golang 使用goroutines和channel异步获取url

package main

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

var urls = []string{
	"http://pulsoconf.co/",
	"http://golang.org/",
	"http://matt.aimonetti.net/",
}

type HttpResponse struct {
	url      string
	response *http.Response
	err      error
}

func asyncHttpGets(urls []string) []*HttpResponse {
	ch := make(chan *HttpResponse, len(urls)) // buffered
	responses := []*HttpResponse{}
	for _, url := range urls {
		go func(url string) {
			fmt.Printf("Fetching %s \n", url)
			resp, err := http.Get(url)
			resp.Body.Close()
			ch <- &HttpResponse{url, resp, err}
		}(url)
	}

	for {
		select {
		case r := <-ch:
			fmt.Printf("%s was fetched\n", r.url)
			responses = append(responses, r)
			if len(responses) == len(urls) {
				return responses
			}
		case <-time.After(50 * time.Millisecond):
			fmt.Printf(".")
		}
	}

	return responses

}

func main() {
	results := asyncHttpGets(urls)
	for _, result := range results {
		fmt.Printf("%s status: %s\n", result.url,
			result.response.Status)
	}
}