limit

defer log.Println("Done")
apiConn := Open()
var wg sync.WaitGroup
wg.Add(20)
for i := 0; i < 10; i++ {
	go func() {
		defer wg.Done()
		if err := apiConn.ReadFile(context.Background()); err != nil {
			log.Println("cannot read file:", err)
			return
		}
		log.Println("read file")
	}()
}
for i := 0; i < 10; i++ {
	go func() {
		defer wg.Done()
		if err := apiConn.ResolveAddress(context.Background()); err != nil {
			log.Println("cannot resolve address:", err)
			return
		}
		log.Println("ResolveAddress")
	}()
}
wg.Wait()