golang_generator_pattern.go

package main

import (
	"log"
	"time"
)

func main() {
	size := 100
	for num := range FibonacciGenerator(size, false) {
		log.Println(num)
	}

	// TimeOut処理 と ChannelのClose検知 と待ち時間中の処理
	receiver := FibonacciGenerator(size, true)
	timeout := time.After(time.Second)
	for {
		select {
		case receive, ok := <-receiver:
			if !ok {
				log.Println("finish")
				return
			}
			log.Println(receive)
		case <-timeout:
			log.Println("timeout")
			return
		default:
			log.Println("wait")
			time.Sleep(time.Duration(100) * time.Millisecond)
		}
	}
}

func FibonacciGenerator(size int, isDelay bool) <-chan int {
	ch := make(chan int)
	a := 0
	b := 1
	tmp := 0

	go func() {
		for i := 0; i < size; i++ {
			ch <- b
			tmp = b
			b = a + b
			a = tmp
			if isDelay {
				time.Sleep(time.Duration(b) * time.Millisecond)
			}
		}
		close(ch)
	}()
	return ch
}