main.go

package main

import (
	"fmt"
	"sync"
)

var x = 0

func sendNumber(wg *sync.WaitGroup, ch chan<- int, nump *int) {
	ch <- *nump + x
	wg.Done()
}

func main() {
	var wg sync.WaitGroup
	var num = 123
	var p = &num

	wg.Add(1)
	ch := make(chan int, 1)
	go sendNumber(&wg, ch, p)

	wg.Wait()
	num = 789
	fmt.Println(<-ch)
}