How to be 100% sure that goroutines are waited on condition?

reading the book Concurrency in Go by Katherine Cox-Buday and there is example how to use Condition.Broadcast to wake up waiting goroutines. here is the example from the book

<!-- language: lang-go -->

package main

import (
	"fmt"
	"sync"
)

type Button struct {
	Clicked *sync.Cond
}

func main() {
	button := &Button{Clicked: &sync.Cond{L: &sync.Mutex{}}}

	subscribe := func(c *sync.Cond, fn func()) {
		var goroutineRunning sync.WaitGroup
		goroutineRunning.Add(1)
		go func() {
			goroutineRunning.Done() //1
			c.L.Lock()
            // 2
			defer c.L.Unlock()
			c.Wait()
			fn()
		}()
		goroutineRunning.Wait()
	}

	var clickedRegistred sync.WaitGroup
	clickedRegistred.Add(2)

	subscribe(button.Clicked, func() {
		fmt.Println("Func #1")
		clickedRegistred.Done()
	})

	subscribe(button.Clicked, func() {
		fmt.Println("Func #2")
		clickedRegistred.Done()
	})

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

is it code 100% concurrency safe?

is it possible situation when main goroutine continue the work and does broadcast before func goroutines parked and waited the signal/broadcast from condition?

I mean the situation when func goroutines done their work at line //1 but did not acquire the condition lock yet and main goroutine do broadcast this time, is it possible?

my assumption the follow: should the line //1 be moved at place //2 to avoid this situation?

or there is no problem and the situation I discribed does not make sence?

Your question has two parts, I think:

1. Does this code have a potential race bug? Yes: see, e.g., https://stackoverflow.com/q/58368947/1256452

2. Is moving the Done call a fix? In this particular code, yes, but I would say, perhaps not a particularly good fix. As Andy Schweig notes in a comment on his own answer, it's more typical for code that uses the condition's Wait method to loop:

   for some_boolean { c.Wait() }
   

   The code that calls c.Signal or c.Broadcast would set the boolean appropriately (here, to false) before calling Signal or Broadcast, to indicate that the waiter should now stop waiting.