// PREDICT: what are the possible outputs? What's the race here even if it
// "usually works"? Run with -race a few times.
package main

import (
	"fmt"
	"sync"
)

func main() {
	var wg sync.WaitGroup
	count := 0
	for i := 0; i < 3; i++ {
		go func() {
			wg.Add(1) // <-- what's wrong with Add here?
			defer wg.Done()
			count++
		}()
	}
	wg.Wait()
	fmt.Println("count:", count)
}