同じジョブは同時実行させないようにしたい。 --> channel bufferでblock

lock-with-channel-buffer.go

package main

import (
	"log"
	// "runtime"
	"sync"
	"time"
)

func worker(jobs ...string) <-chan string {
	var wg sync.WaitGroup
	receiver := make(chan string)

	limit := make(map[string](chan int))
	for _, i := range jobs {
		limit[i] = make(chan int, 1)  // jobs ごとにchannel作成。 buffer=1にすることで重複させないように
	}

	go func() {
		for _, i := range jobs {
			wg.Add(1)
			limit[i] <- 1
			go func(i string) {
				// log.Println("num of goroutine: ", runtime.NumGoroutine())
				receiver <- "start: " + i
				time.Sleep(time.Duration(1) * time.Second)
				receiver <- "end: " + i
				wg.Done()
				<-limit[i]
			}(i)
		}
		wg.Wait()
		close(receiver)
	}()

	return receiver
}

func main() {
	log.Println("[START]")
	defer log.Println("[END]")

	receiver := worker("pen", "pineapple", "apple", "pen")
	for {
		receive, ok := <-receiver
		if !ok {
			log.Println("closed.")
			return
		}
		log.Println(receive)
	}
}

参考にさせてもらった記事

http://jxck.hatenablog.com/entry/20130414/1365960707