Runtime BorderColor is not working in Xcode 9

I made a extension of CALayer for border color as a runtime attribute, but it is not working.

It shows default black color only.

extension CALayer {
    var borderUIColor: UIColor {
        set {
            self.borderColor = newValue.cgColor
        }

        get {
            return UIColor(cgColor: self.borderColor!)
        }
    }
}