atomic_main.go

package main

import (
	"fmt"
	"sync"
	"sync/atomic"
	"time"
)

func main() {
	const (
		numGoroutines = 4
		numIterations = 100000000
	)

	var (
		waitAllStart sync.WaitGroup
		running      sync.WaitGroup

		n int32
	)

	perOpTimes := make([]int64, numGoroutines)
	waitAllStart.Add(numGoroutines)
	running.Add(numGoroutines)
	for i := 0; i < numGoroutines; i++ {
		go func(g int) {
			defer running.Done()
			waitAllStart.Done()
			waitAllStart.Wait()

			started := time.Now()
			for i := 0; i < numIterations; i++ {
				atomic.AddInt32(&n, 1)
			}
			total := time.Since(started)
			perOpTimes[g] = total.Nanoseconds() / numIterations
		}(i)
	}

	running.Wait()
	fmt.Println("Per op (ns):", perOpTimes)
}