latch

package main

import (
	"log"
	"os"
	"sync"
	"time"

	"github.com/devlights/gomy/latch"
)

func main() {
	const (
		latchCount     = 2
		goroutineCount = 4
	)

	var (
		goroutineLog = log.New(os.Stdout, "[goroutine] ", 0)
		waiterLog    = log.New(os.Stdout, "[waiter   ] ", 0)
	)

	var (
		wg sync.WaitGroup
	)

	// make latch
	l := latch.NewCountDownLatch(latchCount)

	// start goroutines
	wg.Add(goroutineCount)
	for i := 0; i < goroutineCount; i++ {
		i := i
		go func() {
			defer func() { wg.Done() }()

			time.Sleep(time.Duration(1+i) * 100 * time.Millisecond)
			goroutineLog.Printf("done [%d]", i)

			l.CountDown()
		}()
	}

	// wait until latch is open
	select {
	case <-l.Await():
		waiterLog.Print("latch opened")
	case <-time.After(goroutineCount * time.Second):
		waiterLog.Print("time over")
	}

	// wait until all goroutine is done
	wg.Wait()

}

Output:

[goroutine] done [0]
[goroutine] done [1]
[waiter   ] latch opened
[goroutine] done [2]
[goroutine] done [3]