package main

​

import (

  "fmt"

  "math/rand"

  "time"

)

​

func worker(id int, jobs <-chan int, results chan<- string) {

  for j := range jobs {

    // do work

    time.Sleep(time.Millisecond * time.Duration(20+rand.Intn(20)))

    results <- fmt.Sprintf("worker %d done job %d", id, j)

  }

}

​

func main() {

  jobs := make(chan int, 8)     // buffer = backpressure control

  results := make(chan string)

​

  // spin up consumers

  for w := 1; w <= 3; w++ { go worker(w, jobs, results) }

​

  // produce jobs

  go func() {

    for j := 1; j <= 12; j++ { jobs <- j }

    close(jobs) // no more work

  }()

​