package main

import (
	"fmt"
	"sync"
)

func main() {
	number := 1

	var wg sync.WaitGroup
	wg.Add(1)

	go func() {
		defer wg.Done()

		number = number * 2 // a., b.
	}()

	wg.Wait()
	// c.

	fmt.Println(number) // d.
}
