How to use Go's sync.Condition

condition.go

// How to use sync.Condition
// https://play.golang.org/p/IdIkQ6S5ZlV
package main

import (
	"fmt"
	"sync"
	"time"
)

func main() {
	var (
		loadWg, finishWg sync.WaitGroup
		mu               sync.Mutex
		cond             = sync.NewCond(&mu)
	)
	for i := 0; i < 5; i++ {
		loadWg.Add(1)
		finishWg.Add(1)
		go func(i int) {
			fmt.Printf("%d waiting\n", i)
			cond.L.Lock()
			loadWg.Done()
			cond.Wait()
			cond.L.Unlock()
			time.Sleep(500 * time.Millisecond)
			fmt.Printf("%d finished\n", i)
			finishWg.Done()
		}(i)
	}
	loadWg.Wait()
	fmt.Println("waking goroutines")
	cond.Broadcast()
	finishWg.Wait()
	fmt.Println("all goroutines finished")
}