iOS tableview设置sectionHeader不悬浮

sectionHeaderHeight为sectionHeader高度

func scrollViewDidScroll(_ scrollView: UIScrollView) {
        let sectionHeaderHeight: CGFloat = 30.0
        if scrollView.contentOffset.y <= sectionHeaderHeight && scrollView.contentOffset.y >= 0 {
            scrollView.contentInset = UIEdgeInsets(top: -scrollView.contentOffset.y, left: 0, bottom: 0, right: 0)
        } else if scrollView.contentOffset.y >= sectionHeaderHeight {
            scrollView.contentInset = UIEdgeInsets(top: -sectionHeaderHeight, left: 0, bottom: 0, right: 0)
        }
    }