任何更好的方式来跟踪goroutine的回应？

Question

我试图让我的头围绕goroutines。我创建了一个简单的程序，可以跨多个搜索引擎并行执行相同的搜索。为了跟踪答复的数量，我计算了我收到的电话号码。虽然这似乎有点业余。

当我从下面的代码中收到所有goroutine的响应时，是否有更好的方式知道？

package main 

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

type Query struct { 
    url string 
    status string 
} 

func search (url string, out chan Query) { 
    fmt.Printf("Fetching URL %s\n", url) 
    resp, err := http.Get(url) 

    if err != nil { 
     log.Fatal(err) 
    } 

    defer resp.Body.Close() 

    out <- Query{url, resp.Status} 
} 

func main() { 
    searchTerm := "carrot" 

    fmt.Println("Hello world! Searching for ", searchTerm) 

    searchEngines := []string{ 
     "http://www.bing.co.uk/?q=", 
     "http://www.google.co.uk/?q=", 
     "http://www.yahoo.co.uk/?q="} 

    out := make(chan Query) 

    for i := 0; i < len(searchEngines); i++ { 
     go search(searchEngines[i] + searchTerm, out) 
    } 

    progress := 0 

    for { 
        // is there a better way of doing this step? 
     if progress >= len(searchEngines) { 
      break 
     } 
     fmt.Println("Polling...") 
     query := <-out 
     fmt.Printf("Status from %s was %s\n", query.url, query.status) 
     progress++ 
    } 
} 

Answer 1

请使用sync.WaitGroup，有在pkg doc

searchEngines := []string{ 
    "http://www.bing.co.uk/?q=", 
    "http://www.google.co.uk/?q=", 
    "http://www.yahoo.co.uk/?q="} 
var wg sync.WaitGroup 
out := make(chan Query) 

for i := 0; i < len(searchEngines); i++ { 
    wg.Add(1) 
    go func (url string) { 
     defer wg.Done() 
     fmt.Printf("Fetching URL %s\n", url) 
     resp, err := http.Get(url) 

     if err != nil { 
      log.Fatal(err) 
     } 

     defer resp.Body.Close() 

     out <- Query{url, resp.Status} 

    }(searchEngines[i] + searchTerm) 

} 
wg.Wait()