package main

import (
  "fmt"
  "sync"
  "time"
)

func main() {

  cities := []string{"London", "Paris", "Berlin", "Rome", "Madrid"}
  channel := make(chan string)
  startMultipleGoRoutines(channel, cities)

  for v := range channel {
    fmt.Println(v)
  }
}

func startMultipleGoRoutines(channel chan<- string, cities []string) {
  defer close(channel)
  var wg sync.WaitGroup
  wg.Add(len(cities))
  for _, v := range cities {
    go func(city string) {
      time.Sleep(time.Second)
      channel <- fmt.Sprintf(v + "1")
      wg.Done()
    }(v)
  }
  wg.Wait()
}