Atomics and sync.Once in Go

Lock-free counters, and one-time initialization.

var (
    hits      atomic.Int64
    setupOnce sync.Once
)

func record() int64 {
    setupOnce.Do(func() {
        hits.Store(0)
    })
    return hits.Add(1)
}

func snapshot() int64 {
    return hits.Load()
}

How it works

1. atomic.Int64 updates safely without a mutex.
2. Add and Load are single atomic operations.
3. sync.Once runs its setup exactly once across goroutines.

Keywords and builtins used here

• func
• int64
• return
• var

The run, in numbers

Lines

15

Characters to type

179

Tokens

54

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 31 seconds.

Type this snippet

Step 4 of 5 in Synchronization, step 17 of 25 in Concurrency.

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