sg3.go

type Singleton struct {
    count int
}

var instance *Singleton

func GetInstance() *Singleton {
    if instance == nil {
        instance = &Singleton{}
    }
    return instance
}

func main() {
    var wg sync.WaitGroup
    wg.Add(10)
    for i := 0; i < 10; i++ {
        go func() {
            defer wg.Done()
            singleton := GetInstance()
            singleton.count++
            fmt.Println(singleton.count)
        }()
    }
    wg.Wait()
}