test go routines parallel run

goprocs.go

package main

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

func makeRange(min, max int) []int {
	a := make([]int, max-min+1)
	for i := range a {
		a[i] = min + i
	}
	return a
}

// https://codereview.stackexchange.com/questions/171311/limiting-the-maximum-amount-of-goroutines-run-simultaneously

func main() {
	inp := makeRange(10, 90)
	var wg sync.WaitGroup
	// Create bufferized channel with size 5
	goroutines := make(chan struct{}, 5)
	// Read data from input channel
	for i, data := range inp {
		// 1 struct{}{} - 1 goroutine
		goroutines <- struct{}{}
		wg.Add(1)
		//fmt.Println(data)
		go func(index int, pdata int, goroutines <-chan struct{}, wg *sync.WaitGroup) {
			// Process data
			time.Sleep(1 * time.Millisecond)
			fmt.Println(index, pdata, len(goroutines))
			// Read from "goroutines" channel to free space for new goroutine
			<-goroutines
			wg.Done()
		}(i, data, goroutines, &wg)
	}

	wg.Wait()
	close(goroutines)
}