package main import ( "fmt" "runtime" "sync" "time" ) var ( n int ) func main() { var wg sync.WaitGroup nCPU := runtime.NumCPU() nIter := 10 for i := 0; i < nCPU; i++ { wg.Add(1) go func() { defer wg.Done() for j := 0; j < nIter; j++ { n++ time.Sleep(time.Microsecond * 10) } }() } wg.Wait() fmt.Printf("n is: %d, expected: %d\n", n, nCPU*nIter) }