chan broadcast

chan1.go

package main

import (
	"fmt"
	"sync"
)

func chanEvent1() {
	ch := make(chan struct{})
	var wg sync.WaitGroup

	defer wg.Wait()
	defer close(ch)

	for i := 0; i < 5; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			defer fmt.Printf("%d: chan closed\n", i)

			<-ch
		}(i)
	}
}

chan2.go

package main

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

type Object struct {
	notify chan struct{}
	l      sync.Mutex
}

func (o *Object) Notify() <-chan struct{} {
	o.l.Lock()
	defer o.l.Unlock()

	if o.notify == nil {
		o.notify = make(chan struct{}, 5)
	}

	return o.notify
}

func (o *Object) Done() {
	if o.notify != nil {
		o.l.Lock()
		defer o.l.Unlock()

		close(o.notify)
		o.notify = nil
	}
}

func chanEvent2() {
	var o Object
	var wg sync.WaitGroup

	defer wg.Wait()
	defer o.Done()

	for i := 0; i < 5; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			defer fmt.Printf("%d: chan closed\n", i)

			<-o.Notify()
		}(i)
	}

	time.Sleep(time.Millisecond)
}

main.go

package main

func main() {
	for i := 0; i < 5; i++ {
		chanEvent1()
	}
}