Playing with WaitGroup in nested goroutines

wait-groups.go

package main

import (
	"crypto/rand"
	"fmt"
	"math/big"
	"os"
	"sync"
	"time"
)

// a little test of nested wait groups.... does it behave as I expect?
func main() {
	numWorkers := 4
	numTasks := 4

	// start workers in goroutine
	var workersWG sync.WaitGroup
	for i := 0; i < numWorkers; i++ {
		i := i
		fmt.Println("Worker", i, ": START")

		workersWG.Add(1)
		go func() {
			defer workersWG.Done()

			// start tasks in worker
			var tasksWG sync.WaitGroup
			for j := 0; j < numTasks; j++ {
				j := j
				fmt.Println("Worker ", i, " | Task ", j, ": START")
				tasksWG.Add(1)
				go func() {
					defer tasksWG.Done()

					dur, _ := rand.Int(rand.Reader, big.NewInt(5000000000))
					time.Sleep(time.Duration(dur.Int64()))
					fmt.Println("Worker ", i, " | Task ", j, ": END")
				}()
			}

			tasksWG.Wait()
			time.Sleep(5000000000) //apparently this is 5 sec
			fmt.Println("Worker", i, ": END")
		}()
	}

	workersWG.Wait()
	os.Exit(0)
}