使用CALayer底部边框向下滑动UIView

I'm attempting to slide a UIView down when a bar button is clicked. So far, so good, but I've run into an issue. For aesthetics, I've added a bottom border to the view, and I want to animate this bottom border with the UIView sliding animation. The problem is that the CABasicAnimation is limited, not allowing for a CurveEaseIn. So, the bottom border slides quicker than the UIView. I'm attempting to slide a UIView down when a ba