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54 lines
967 B
Markdown
54 lines
967 B
Markdown
---
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date: 2020-09-18
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id: 53c0ad13-0c19-4a84-9c67-cc31d036be4d
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title: Golang WaitGroup
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---
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# Description
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A [WaitGroup](https://golang.org/pkg/sync/#WaitGroup) waits for a
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collection of goroutines to finish. The main goroutine calls Add to set
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the number of goroutines to wait for. Then each of the goroutines runs
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and calls Done when finished. At the same time, Wait can be used to
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block until all goroutines have finished.
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A WaitGroup must not be copied after first use.
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# Syntax
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``` go
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type Counter struct {
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mu sync.Mutex
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value int
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}
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func (c *Counter) Inc() {
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c.mu.Lock()
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defer c.mu.Unlock()
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c.value++
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}
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func (c *Counter) Value() int {
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return c.value
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}
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func NewCounter() *Counter {
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return &Counter{}
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}
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wantedCount := 1000
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counter := NewCounter()
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var wg sync.WaitGroup
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wg.Add(wantedCount)
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for i := 0; i < wantedCount; i++ {
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go func(w *sync.WaitGroup) {
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counter.Inc()
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w.Done()
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}(&wg)
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}
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wg.Wait()
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```
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