get rid of the space under the text of UITextView - swift

Question

I'm currently working on making a custom UITextView class.
As you can see in the image, there is bigger space between the text in line 1 and line 2.
The blue cursor represents the height of the text, however, like line 2's text, the gray background has a height around 2 times bigger than the text.
After some research, I thought change the NSMutableParagraphStyle's lineSpacing will fix the problem I have (but it didn't). Is changing the lineSpacing or MutableParagraphStyle won't change the line-height?
import UIKit
class CustomTextView: UITextView {
override init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
configure()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
init() {
super.init(frame: .zero, textContainer: nil)
configure()
}
private func configure() {
translatesAutoresizingMaskIntoConstraints = false
font = UIFont.myCustomFont()
let textStyle = NSMutableParagraphStyle()
textStyle.lineSpacing = 1.0
textStyle.paragraphSpacing = 1.0
let attributes: Dictionary = [NSAttributedString.Key.paragraphStyle: textStyle]
attributedText = NSAttributedString(string: self.text, attributes: attributes)
}
override func caretRect(for position: UITextPosition) -> CGRect {
var superRect = super.caretRect(for: position)
guard let font = self.font else { return superRect }
superRect.size.height = font.pointSize
return superRect
}
}
Added this part later...
So, when I delete the line for setting the font, I was able to get rid of the bigger space (but lost the custom font).
So I think the custom font has something like a bottom padding? I guess. I created a font like this, but do you see any problem or any clue why I get the bottom space, like the gray area in the image?
extension UIFont {
static func myCustomFont() -> UIFont {
return UIFont(name: "Custom Font", size: 18)!
}
}