How to use Golang sync/cond

cond.go

package main

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

func main() {
	c := sync.NewCond(&sync.Mutex{})
	wg := &sync.WaitGroup{}

	fmt.Printf("M: launching 'waiters'\n")

	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			fmt.Printf("%d: waiting cond\n", i)
			c.L.Lock()
			defer c.L.Unlock()
			c.Wait()
			fmt.Printf("%d: released\n", i)
		}(i)
	}

	fmt.Printf("M: waiting 2s\n")
	time.Sleep(2 * time.Second)

	for i := 0; i < 3; i++ {
		fmt.Printf("M: signal and wait 2s\n")
		c.Signal()
		time.Sleep(2 * time.Second)
	}

	fmt.Printf("M: broadcasting\n")
	c.Broadcast()

	fmt.Printf("M: waiting 'waiters' to finish\n")
	wg.Wait()

	fmt.Printf("M: waiting 2s\n")
	time.Sleep(2 * time.Second)
}