UIImagePickerController not asking for permission

I have implemented the following code in an app to allow the user to add an image to the app. However the user is never asked for permission to access photo's. What am I missing here?

in my info.plist I have set: Privacy - Photo Library Usage Description = Please provide access to your photo library

The bundle identifier is: $(PRODUCT_BUNDLE_IDENTIFIER)

import UIKit

class NewPostXIB: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

@IBOutlet weak var image: UIImageView!

let imagePicker = UIImagePickerController()

override func viewDidLoad() {
    super.viewDidLoad()
    imagePicker.delegate = self
}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    self.view.endEditing(true)
}

@IBAction func closeButton(_ sender: Any) {
    dismiss(animated: false, completion: nil)
}

@IBAction func addImageButton(_ sender: Any) {
    if UIImagePickerController.isSourceTypeAvailable(.photoLibrary) {
        imagePicker.allowsEditing = true
        imagePicker.sourceType = .photoLibrary
        present(imagePicker, animated: true, completion: nil)
        }
}

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    if let pickedImage = info[UIImagePickerControllerEditedImage] as? UIImage {
        image.contentMode = .scaleAspectFill
        image.image = pickedImage
    }
    dismiss(animated: false, completion: nil)
}

func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
    dismiss(animated: true, completion: nil)
}

Adding the following function solved the problem:

 func checkPermission() {
    let photoAuthorizationStatus = PHPhotoLibrary.authorizationStatus()
    switch photoAuthorizationStatus {
    case .authorized:
        present(imagePicker, animated: true, completion: nil)
        print("Access is granted by user")
    case .notDetermined:
        PHPhotoLibrary.requestAuthorization({
            (newStatus) in
            print("status is \(newStatus)")
            if newStatus ==  PHAuthorizationStatus.authorized {
                /* do stuff here */
                self.present(self.imagePicker, animated: true, completion: nil)
                print("success")
            }
        })
        print("It is not determined until now")
    case .restricted:
        // same same
        print("User do not have access to photo album.")
    case .denied:
        // same same
        print("User has denied the permission.")
    }
}