urlBuff simulates downloads with timers. It has four workers that continuously pull from the urlChannel until everything is done

urlBuff.go

package main

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

func randInt(min int, max int) int {
  return min + rand.Intn(max-min)
}

//go downloadUrl(urlChan, doneChan)
func downloadUrl(urlChan chan int, doneChan chan string) {
  secs := randInt(1,10)
  u := <-urlChan
  u_str := strconv.Itoa(u)
  fmt.Println("Url: " + u_str  +   " launched for: " + strconv.Itoa(secs))
  select {
      case <-time.After(time.Second * time.Duration(secs)):
      fmt.Println("[" + u_str +  "] timer done")
  }

  doneChan <- "[" + u_str + "] done"
  downloadUrl(urlChan, doneChan)
  return
}


func main() {
  rand.Seed(time.Now().UnixNano())
  urlChan := make(chan int, 100)
  doneChan := make(chan string, 4) // Because we have 4 workers

  // All the task urls to download go here
  fmt.Println("Initialize the tasks...")
  for i := range make([]int, 10)  {
   urlChan <- i
  }

  // This is your worker pool, they pull
  // the next taskUrl off the masterChannel
  fmt.Println("Initialize the workers...")
  for worker := range make([]int, 4) {
    fmt.Println("[worker]", worker)
    go downloadUrl(urlChan, doneChan)
  }

  // Done counter so we break out
  i := 0;
  // Read everything off the doneChan
  fmt.Println("Wait for it all..")
  for j := range doneChan {
        fmt.Println("[DONE]", j)
        i++
        if(i == 10) { //dont break until all 10 gathered
          break
        }
  }
  fmt.Println("ok, done")
}