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-rw-r--r--src/sync/example_test.go59
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+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sync_test
+
+import (
+ "fmt"
+ "sync"
+)
+
+type httpPkg struct{}
+
+func (httpPkg) Get(url string) {}
+
+var http httpPkg
+
+// This example fetches several URLs concurrently,
+// using a WaitGroup to block until all the fetches are complete.
+func ExampleWaitGroup() {
+ var wg sync.WaitGroup
+ var urls = []string{
+ "http://www.golang.org/",
+ "http://www.google.com/",
+ "http://www.example.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()
+}
+
+func ExampleOnce() {
+ var once sync.Once
+ onceBody := func() {
+ fmt.Println("Only once")
+ }
+ done := make(chan bool)
+ for i := 0; i < 10; i++ {
+ go func() {
+ once.Do(onceBody)
+ done <- true
+ }()
+ }
+ for i := 0; i < 10; i++ {
+ <-done
+ }
+ // Output:
+ // Only once
+}