Golang中的sync.WaitGroup用法实例

var wg sync.WaitGroup 
var urls = []string{ 
  "http://www.golang.org/", 
  "http://www.google.com/", 
  "http://www.somestupidname.com/", 
} 
for _, url := range urls { 
  // Increment the WaitGroup counter. 
  wg.Add(1) 
  // Launch a goroutine to fetch the URL. 
  go func(url string) { 
    // Decrement the counter when the goroutine completes. 
    defer wg.Done() 
    // Fetch the URL. 
    http.Get(url) 
  }(url) 
} 
// Wait for all HTTP fetches to complete. 
wg.Wait()

 

package main

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

const ( 
  num = 10000000 
)

func main() { 
  TestFunc("testchan", TestChan) 
}

func TestFunc(name string, f func()) { 
  st := time.Now().UnixNano() 
  f() 
  fmt.Printf("task %s cost %d \r\n", name, (time.Now().UnixNano()-st)/int64(time.Millisecond)) 
}

func TestChan() { 
  var wg sync.WaitGroup 
  c := make(chan string) 
  wg.Add(1)

  go func() { 
    for _ = range c { 
    } 
    wg.Done() 
  }()

  for i := 0; i < num; i++ { 
    c <- "123" 
  }

  close(c) 
  wg.Wait()

}