Calculate primes using Doug McIlroy's idea: http://swtch.com/~rsc/thread/

primes.go

package main

import "sync"

func primes() {
	var recur func(ch chan int)
	wg := sync.WaitGroup{}

	recur = func(ch chan int) {
		p := <-ch
		newch := make(chan int)
		println(p)

		wg.Add(1)
		go recur(newch)

		for n := range ch {
			if n%p != 0 {
				newch <- n
			}
		}
		close(newch)
		wg.Done()

	}

	ch := make(chan int)

	go recur(ch)

	for i := 3; i < 135; i++ {
		ch <- i
	}
	close(ch)
	wg.Wait()
}

func main() {
	primes()
}