Using channels and waitgroups for effective communication with goroutines

channels_and_waitgroups.go

package main

import (
	"fmt"
	"sync"
)

// Send words onto a channel until we receive on the done channel
func emit(wch chan string, dch chan struct{}, wg *sync.WaitGroup) {
	words := []string{"The", "quick", "brown", "fox"}
	i := 0
	for {
		select { // Perform an operation on a channel that is not blocked
		case wch <- words[i]: // queue up a word if channel can receive
			i += 1
			if i == len(words) { wch <- "\n"; i = 0 } // there is no limit
		case <- dch: // Is there anything on the done channel or is it closed?
			fmt.Println("\nDone message rcx'd")
			wg.Done()
			return
		}
	}
}

func main() {
	word_ch := make(chan string)
	done_ch := make(chan struct{})
	var wg sync.WaitGroup

	wg.Add(1)
	go emit(word_ch, done_ch, &wg) // start the word pump // Waitgroup must be passed by reference

	for i := 0; i < 15; i++ {
		fmt.Printf("%s ", <- word_ch) // pull a word off the channel
	}
	close(done_ch) // Once we close this channel, it can be received from so it signals any listening goroutines.
	wg.Wait()
}

Thanks to John Graham and Dave Cheney for the tutorials.