worker.go

package main

import (
  "log"
  "sync"
)

type Job struct {
  source int
}

type Result struct {
  Job
  target int
}

var jobs = make(chan Job, 10)
var results = make(chan Result, 10)

func worker(w *sync.WaitGroup) {
  for job := range jobs {
    results <- Result{job, job.source * 2}
  }
  
  w.Done()
}

func allocate(n int) {
  for i := 0; i < n; i++ {
    jobs <- Job{i}
  }
  close(jobs)
}

func result(done chan bool) {
  for result := range results {
    log.Println(result.source, " ", result.target)
  }
  done <- true
}

func createWorkerPool(n int) {
  var w sync.WaitGroup
  for i := 0; i < n; i++ {
    w.Add(1)
    go worker(&w)
  }
  w.Wait()
  close(results)
}

func main() {
  var done = make(chan bool, 1)
  go allocate(10)
  go result(done)
  createWorkerPool(2)
  <- done
}