eac6776159
Remove an ambiguous part of the comment that can cause confusion - passing a WaitGroup by pointer is always mandatory.
56 lines
1.4 KiB
Go
56 lines
1.4 KiB
Go
// To wait for multiple goroutines to finish, we can
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// use a *wait group*.
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package main
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import (
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"fmt"
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"sync"
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"time"
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)
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// This is the function we'll run in every goroutine.
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func worker(id int) {
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fmt.Printf("Worker %d starting\n", id)
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// Sleep to simulate an expensive task.
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time.Sleep(time.Second)
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fmt.Printf("Worker %d done\n", id)
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}
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func main() {
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// This WaitGroup is used to wait for all the
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// goroutines launched here to finish. Note: if a WaitGroup is
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// explicitly passed into functions, it should be done *by pointer*.
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var wg sync.WaitGroup
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// Launch several goroutines and increment the WaitGroup
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// counter for each.
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for i := 1; i <= 5; i++ {
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wg.Add(1)
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// Avoid re-use of the same `i` value in each goroutine closure.
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// See [the FAQ](https://golang.org/doc/faq#closures_and_goroutines)
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// for more details.
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i := i
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// Wrap the worker call in a closure that makes sure to tell
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// the WaitGroup that this worker is done. This way the worker
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// itself does not have to be aware of the concurrency primitives
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// involved in its execution.
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go func() {
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defer wg.Done()
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worker(i)
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}()
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}
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// Block until the WaitGroup counter goes back to 0;
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// all the workers notified they're done.
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wg.Wait()
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// Note that this approach has no straightforward way
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// to propagate errors from workers. For more
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// advanced use cases, consider using the
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// [errgroup package](https://pkg.go.dev/golang.org/x/sync/errgroup).
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}
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