swift how to wait in a loop
override func viewDidLoad() {
    super.viewDidLoad()
    let myGroup = DispatchGroup()
    for i in 0 ..< 5 {
        myGroup.enter()
        Alamofire.request("https://httpbin.org/get", parameters: ["foo": "bar"]).responseJSON { response in
            print("Finished request \(i)")
            myGroup.leave()
        }
    }
    myGroup.notify(queue: .main) {
        print("Finished all requests.")
    }
}