mutex Mutex

package main

import (
    "fmt"
    "sync"
)

type Counter struct {
    mu    sync.Mutex
    count int
}

func (c *Counter) Inc() {
    c.mu.Lock()
    defer c.mu.Unlock()
    c.count++
}

func (c *Counter) Value() int {
    c.mu.Lock()
    defer c.mu.Unlock()
    return c.count
}

func main() {
    c := &Counter{}
    var wg sync.WaitGroup
    for i := 0; i < 100; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            c.Inc()
        }()
    }
    wg.Wait()
    fmt.Println(c.Value())
}