wiki/content/20200918174548-waitgroup.md

date	id	title
2020-09-18	53c0ad13-0c19-4a84-9c67-cc31d036be4d	Golang WaitGroup

Description

A WaitGroup waits for a collection of goroutines to finish. The main goroutine calls Add to set the number of goroutines to wait for. Then each of the goroutines runs and calls Done when finished. At the same time, Wait can be used to block until all goroutines have finished.

A WaitGroup must not be copied after first use.

Syntax

type Counter struct {
    mu    sync.Mutex
    value int
}

func (c *Counter) Inc() {
    c.mu.Lock()
    defer c.mu.Unlock()

    c.value++
}

func (c *Counter) Value() int {
    return c.value
}

func NewCounter() *Counter {
    return &Counter{}
}

wantedCount := 1000
counter := NewCounter()

var wg sync.WaitGroup
wg.Add(wantedCount)

for i := 0; i < wantedCount; i++ {
    go func(w *sync.WaitGroup) {
        counter.Inc()
        w.Done()
    }(&wg)
}

wg.Wait()