cellForRowAtIndexPath being called very late - ios

Question

I am trying to fetch JSON data from OpenWeatherMap API depending on user location and display it in a tableview.
First, I just init my table view :
init(_ coder: NSCoder? = nil) {
self.tableView = UITableView()
self.locationManager = CLLocationManager()
}
Then in viewDidLoad I call a function launchLocationOperations() to get user's location :
func launchLocationOperations() {
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.requestAlwaysAuthorization()
locationManager.startUpdatingLocation()
}
In my delegate :
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
self.locationManager.stopUpdatingLocation()
let locationArray = locations as NSArray
let currentLocation = locationArray.lastObject as! CLLocation
if self.currentCoordinates == nil ||
(self.currentCoordinates?.latitude != currentLocation.coordinate.latitude
||
self.currentCoordinates?.longitude != currentLocation.coordinate.longitude) {
self.currentCoordinates = currentLocation.coordinate
self.hasLoadedCoordinates = true
self.fetchWeatherInformations()
}
}
Then calling fetchWeatherInformation() :
func fetchWeatherInformations() {
// I build my path
let urlPath = StringUtils.buildUrl(self.currentCoordinates)
guard let url = URL(string: urlPath) else { return }
let request = URLRequest(url: url)
URLSession.shared.dataTask(with: request) { data, _, error in
do {
let jsonResponse = try data?.toJSON() as? [String : Any]
self.openWeatherMapResponse = OpenWeatherMapResponse.convert(jsonResponse: jsonResponse)
self.displayUI()
} catch {
print("Error while fetching JSON response : \(error.localizedDescription)")
}
}.resume()
}
And in displayUI() :
func displayUI() {
tableView.delegate = self
tableView.dataSource = self
}
So I have two problems here :
First, didUpdateLocations is being called many times even if I ask to stopUpdatingLocation() when entering the function.
Second, cellForRowAtIndexPath is being called very, very late, like 5 seconds late. I don't know why it is happening because the other dataSource/delegate methods are called instantly after entering displayUI()...
Thanks for your help.