Atomic Number

For simple counter, sync/atomic can be used instead of Mutex.

package main

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

func main() {
	var d atomic.Uint32
	var wg sync.WaitGroup
	wg.Add(100)

	for range 100 {
		go func() {
			d.Add(1)
			wg.Done()
		}()
	}

	wg.Wait()
	fmt.Println(d.Load())
}