Shadow discoloring the navigation bar - ios

Question

The shadow is appearing on top of the navigation bar. Is there anyway to move the shadow underneath the bar or add some code so it doesn't discolor the bar?
This is the code I use in my navigation controller:
import UIKit
class navigationController:UINavigationController, UIViewControllerTransitioningDelegate{
override func viewDidLoad()
{
var appblue = UIColor(red: 109/255, green: 208/255, blue:247/255, alpha: 1.0)
self.navigationBar.barTintColor = appblue
self.navigationBar.layer.masksToBounds = false
self.navigationBar.layer.shadowColor = UIColor.black.cgColor
self.navigationBar.layer.shadowOpacity = 0.7
self.navigationBar.layer.shadowOffset = CGSize(width: 0, height: 2.0)
self.navigationBar.layer.shadowRadius = 4
}
}
and this is what it looks like:
When it should be this color:
Any suggestions?
This is what im trying to make it look like(photo shopped picture):
(the top bar bottom shadow while retaining the second bars color)

Answer 1

Added a image view with a gradient to the bottom of the bar to accomplish what I was going for, Thanks to #Anbu.Karthik for linking another question that I was able to adapt. This is my current code:
import UIKit
class navigationController:UINavigationController, UIViewControllerTransitioningDelegate{
override func viewDidLoad()
{
var appblue = UIColor(red: 109/255, green: 208/255, blue:247/255, alpha: 1.0)
self.navigationBar.barTintColor = appblue
self.navigationBar.layer.masksToBounds = false
var yPosition = self.navigationBar.layer.frame.height
var rectWidth = self.navigationBar.layer.frame.width
let gradient = CAGradientLayer()
let bottomShadow: UIImageView = UIImageView()
bottomShadow.frame = CGRect(x: 0, y: yPosition, width: rectWidth, height: 8)
gradient.frame = bottomShadow.bounds
gradient.colors = [UIColor.lightGray.cgColor, UIColor(white: 1, alpha: 0).cgColor]
navigationBar.addSubview(bottomShadow)
bottomShadow.layer.insertSublayer(gradient, at: 0)
}
}