example_test.go

Documentation: sync

		 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  }
		60
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