Graceful shutdown in Go

A done channel, closed once, tells every worker to stop.

func workUntilDone(jobs <-chan int, done <-chan struct{}) []int {
    var (
        mu      sync.Mutex
        handled []int
        wg      sync.WaitGroup
    )

    for range 3 {
        wg.Go(func() {
            for {
                select {
                case job, ok := <-jobs:
                    if !ok {
                        return
                    }
                    mu.Lock()
                    handled = append(handled, job)
                    mu.Unlock()
                case <-done:
                    return
                }
            }
        })
    }

    wg.Wait()
    return handled
}

How it works

1. Closing a channel broadcasts: every receiver wakes.
2. Workers select on their work and on done.
3. Wait for them before returning, or you leak goroutines.

Keywords and builtins used here

• append
• case
• chan
• for
• func
• if
• int
• range
• return
• select
• struct
• var

The run, in numbers

Lines

28

Characters to type

326

Tokens

100

Three-star pace

110 tpm

At the three-star pace of 110 tokens a minute, this run takes about 55 seconds.

Type this snippet

Step 5 of 5 in Patterns, step 23 of 25 in Concurrency.

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