package main

import (
    "fmt"
    "sync"
)

func add(count *int, wg *sync.WaitGroup, lock *sync.Mutex) {
    defer wg.Done()
    for i := 0; i < 1000; i++ {
        lock.Lock()
        *count = *count + 1
        lock.Unlock()
    }
}

func main() {

    var wg sync.WaitGroup
    lock := &sync.Mutex{}
    wg.Add(3)
    var count int
    go add(&count, &wg, lock)
    go add(&count, &wg, lock)
    go add(&count, &wg, lock)
    wg.Wait()
    fmt.Println(count)

}