Example of sequential channels in Go

sequential-channels.go

package bakery

import (
	"fmt"
	"time"
)

type Order = int

type Cake struct {
	orderId   Order
	baked     bool
	decorated bool
	packed    bool
}

// Create channels
var orders = make(chan Order)
var baked = make(chan *Cake)
var decorated = make(chan *Cake)
var packed = make(chan *Cake)

// baker receives order messages and sends out cake messages
func baker(baked chan<- *Cake, orders <-chan Order) {
	defer close(baked)

	for order := range orders {
		cake := new(Cake)
		cake.orderId = order
		cake.baked = true
		baked <- cake
	}
}

// decorator receives and sends out cake messages
func decorator(decorated chan<- *Cake, cooked <-chan *Cake) {
	defer close(iced)

	for cake := range cooked {
		cake.decorated = true
		decorated <- cake
	}
}

// packer receives and sends out cake messages
func packer(packed chan<- *Cake, decorated <-chan *Cake) {
	defer close(packed)

	for cake := range decorated {
		cake.packed = true
		packed <- cake
	}
}

func main() {
	done := make(chan bool)

	// Start workers
	go baker(baked, orders)
	go decorator(decorated, baked)
	go packer(packed, decorated)

	// Log finished cakes
	go func() {
		for cake := range packed {
			fmt.Printf("Cake #%d is ready\n", cake.orderId)
		}

		done <- true
	}()

	// Send orders
	go func() {
		defer close(orders)

		// Send an order every 1 second
		for n := range 10 {
			orders <- n + 1
			time.Sleep(1 * time.Second)
		}
	}()

	// Wait for the done message
	<-done
}