package main

// To wait for multiple goroutines to finish, we can use a wait group

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

// This is the function we'll run in every goroutine
func worker(id int) {
	fmt.Printf("Worker %d starting\n", id)
	time.Sleep(time.Second)
	fmt.Printf("Worker %d done\n", id)
}

func main() {
	// This WaitGroup is used to wait for all the goroutines
	// launched here to finish.
	var wg sync.WaitGroup

	// launch several goroutines and increment the WaitGroup counter
	// for each
	for i := 1; i <= 5; i++ {
		wg.Add(1)

		// Wrap the worker call in a closure that makes sure to tell
		// the WaitGroup that this worker is done.
		// This way the worker itself does not have to be aware of
		// the concurrency primitives involved in its execution.
		go func() {
			// defer statement executed, and places
			// wg.Done() on a list to be executed prior to the function returning
			defer wg.Done()
			worker(i)
		}()
	}

	// Block until the WaitGroup counter goes back to 0
	// all the workers notified they're done
	wg.Wait()
}