Errata Concurrency in Go chapter 3, page 56

deadlock.go

package main

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

type Button struct {
	Clicked *sync.Cond
}

func main() {
	button := Button {Clicked: sync.NewCond(&sync.Mutex{})}
	subscribe := func(c *sync.Cond, fn func()) {
		var goroutineRunning sync.WaitGroup
		goroutineRunning.Add(1)
		go func() {
			goroutineRunning.Done()
			// Simulating a delay during the execution of the goroutine  <----------------------------------
			time.Sleep(1 * time.Second)
			c.L.Lock()
			defer c.L.Unlock()
			c.Wait()
			fn()
		}()
		goroutineRunning.Wait()
	}
	var clickRegistered sync.WaitGroup
	clickRegistered.Add(3)
	subscribe(button.Clicked, func() {
		fmt.Println("Maximizing window.")
		clickRegistered.Done()
	})
	subscribe(button.Clicked, func() {
		fmt.Println("Displaying annoying dialog box!")
		clickRegistered.Done()
	})
	subscribe(button.Clicked, func() {
		fmt.Println("Mouse clicked.")
		clickRegistered.Done()
	})

	button.Clicked.Broadcast()
	clickRegistered.Wait()
}