package main

import (
	"fmt"
	"math/rand"
	"sync"
	"time"
)

var mu sync.Mutex

type queue struct {
	size int
	load []int
}

func remove(s []int, i int) []int {
	copy(s[i:], s[i+1:])
	return s[:len(s)-1]
}

func work(q *queue) <-chan string {
	ch := make(chan string)
	go func() {
		for {
			mu.Lock()
			curLoad := len(q.load)
			mu.Unlock()
			if curLoad > 0 {
				mu.Lock()
				curValue := q.load[0]
				mu.Unlock()
				time.Sleep(time.Millisecond * time.Duration(curValue))
				mu.Lock()
				q.load = remove(q.load, 0)
				mu.Unlock()
				ch <- "finished"
			}
		}
	}()
	return ch
}

func load(q *queue) {
	go func() {
		for {
			time.Sleep(time.Millisecond * time.Duration(rand.Intn(1000)))
			mu.Lock()
			q.load = append(q.load, rand.Intn(1000))
			mu.Unlock()
		}
	}()
}

func init() {
	rand.Seed(time.Now().UnixNano())
}

func main() {
	q := queue{
		size: 10,
	}
	load(&q)
	ch := work(&q)
	for {
		select {
		case <-ch:
			fmt.Println("finished something")
		}
	}
}