sequential_fan_in.go

package main

import (
	"fmt"
	"sync"
)

type Message struct {
	msg  string
	wait chan bool
}

func BoringSyncedGenerator(msg string) <-chan Message {
	m := make(chan Message)

	go func() {
		for i := 0; ; i++ {
			wait := make(chan bool)
			m <- Message{msg: fmt.Sprintf("%s %d", msg, i), wait: wait}
			<-wait
		}
	}()
	return m
}

func BoringSequentialFanIn(syncedChans ... <-chan Message) <-chan string {
	c := make(chan string)

	go func() {
		msgs := make([]Message, len(syncedChans))
		wg := sync.WaitGroup{}
		wg.Add(len(syncedChans))
		for i, v := range syncedChans {
			go func(idx int, x <-chan Message) {
				msgs[idx] = <-x
				wg.Done()
			} (i, v)
		}

		wg.Wait()

		for _, v := range msgs {
			c <- v.msg
		}

		for _, v := range msgs {
			v.wait <- true
		}
	}()

	return c
}