libgo/go/sync/example_test.go

   1 // Copyright 2012 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package sync_test
   6
   7 import (
   8         "fmt"
   9         "sync"
  10 )
  11
  12 type httpPkg struct{}
  13
  14 func (httpPkg) Get(url string) {}
  15
  16 var http httpPkg
  17
  18 // This example fetches several URLs concurrently,
  19 // using a WaitGroup to block until all the fetches are complete.
  20 func ExampleWaitGroup() {
  21         var wg sync.WaitGroup
  22         var urls = []string{
  23                 "http://www.golang.org/",
  24                 "http://www.google.com/",
  25                 "http://www.somestupidname.com/",
  26         }
  27         for _, url := range urls {
  28                 // Increment the WaitGroup counter.
  29                 wg.Add(1)
  30                 // Launch a goroutine to fetch the URL.
  31                 go func(url string) {
  32                         // Decrement the counter when the goroutine completes.
  33                         defer wg.Done()
  34                         // Fetch the URL.
  35                         http.Get(url)
  36                 }(url)
  37         }
  38         // Wait for all HTTP fetches to complete.
  39         wg.Wait()
  40 }
  41
  42 func ExampleOnce() {
  43         var once sync.Once
  44         onceBody := func() {
  45                 fmt.Println("Only once")
  46         }
  47         done := make(chan bool)
  48         for i := 0; i < 10; i++ {
  49                 go func() {
  50                         once.Do(onceBody)
  51                         done <- true
  52                 }()
  53         }
  54         for i := 0; i < 10; i++ {
  55                 <-done
  56         }
  57         // Output:
  58         // Only once
  59 }