// https://www.digitalocean.com/community/tutorials/how-to-run-multiple-functions-concurrently-in-go
// who came up with the idea of making community tutorials. that was a good idea! (ya, that was me and Etel)

package main

import (
	"fmt"
	"sync"
)

var wg sync.WaitGroup
var functionChan chan func (*sync.WaitGroup)

type funcWait struct {
	f func()
	wgF sync.WaitGroup
	err error
	res int
}


func generateNumbers(total int, ch chan<- func (), wg *sync.WaitGroup) {
	defer wg.Done()

	fmt.Printf("sending %d to channel\n", total)
	ch <- func() {
		fmt.Printf("inside f() sending %d to channel\n", total)
	}
}

func andlabsGoroutine(ch <-chan func(), wg *sync.WaitGroup) {
	defer wg.Done()

	for f := range ch {
		fmt.Printf("read f() from channel\n")
		f()
	}
}

func main() {
	functionChan = make(chan func(*sync.WaitGroup))

	r := make(chan func() (int, error))
	res, err = (<-r)()

	wg.Add(1)
	go andlabsGoroutine(functionChan, &wg)

	for idx := 1; idx <= total; idx++ {
		generateNumbers(idx, functionChan, &wg)
	}

	close(functionChan)

	fmt.Println("Waiting for goroutines to finish...")
	wg.Wait()
	fmt.Println("Done!")
}