PushViewController Twice When I double click too quickly

I have the follow code when I call to push the ViewController to detailed chat controller ( 1-to-1 chat). However, if I click too quickly, the view controller will be pushed twice. I see the animation twice. Could anyone point me where the mistake is? The code is from a Youtube lesson (Firebase Chat) from LBTA.

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let message = messages[indexPath.row]
    guard let chatPartnerId = message.chatPartnerId() else {return}

    let ref = Database.database().reference().child("users").child(chatPartnerId)
    ref.observeSingleEvent(of: .value, with: { (snapshot) in
        guard let dictionary = snapshot.value as? [String: AnyObject] else {
            return
        }
        let user = ChatUser(dictionary: dictionary)
        user.id = chatPartnerId
        self.showChatControllerForUser(user)

    }, withCancel: nil)

}

func showChatControllerForUser(_ user: ChatUser) {
    let chatLogController = ChatLogController(collectionViewLayout: UICollectionViewFlowLayout())
    chatLogController.chatUser = user
    navigationController?.pushViewController(chatLogController, animated: true)
}

What you could do to avoid this issue is to disable the table view user interaction and reenable it after pushing to second view controller.

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    // add this:
    tableView.isUserInteractionEnabled = false
    let message = messages[indexPath.row]
    guard let chatPartnerId = message.chatPartnerId() else {return}

    let ref = Database.database().reference().child("users").child(chatPartnerId)
    ref.observeSingleEvent(of: .value, with: { (snapshot) in
        guard let dictionary = snapshot.value as? [String: AnyObject] else {
            return
        }
        let user = ChatUser(dictionary: dictionary)
        user.id = chatPartnerId
        self.showChatControllerForUser(user)

    }, withCancel: nil)

}

func showChatControllerForUser(_ user: ChatUser) {
    let chatLogController = ChatLogController(collectionViewLayout: UICollectionViewFlowLayout())
    chatLogController.chatUser = user
    // edit this:
    navigationController?.pushViewController(chatLogController, animated: true)

    navigationController?.pushViewController(chatLogController, animated: true, completion: {
        self.tableView.isUserInteractionEnabled = true
    })
}

By default, pushViewController(_:animated:) does not has a completion handler, so as a workaround we could add the follwoing extention to achieve it:

extension UINavigationController {
    public func pushViewController(
        _ viewController: UIViewController,
        animated: Bool,
        completion: @escaping () -> Void)
    {
        pushViewController(viewController, animated: animated)

        guard animated, let coordinator = transitionCoordinator else {
            DispatchQueue.main.async { completion() }
            return
        }

        coordinator.animate(alongsideTransition: nil) { _ in completion() }
    }
}

_{Cited from: https://stackoverflow.com/a/33767837/5501940}