This adds a "done" button to your keyboard toolbar.

keyboardextension.swift

//Modified from:
//http://swiftquickstart.blogspot.com/2016/10/adding-done-button-to-keyboard.html
extension UITextField {
    func addKeyboardDoneButton() {
        let keyboardToolBar = UIToolbar()
        keyboardToolBar.sizeToFit()
         
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem:
            UIBarButtonItem.SystemItem.flexibleSpace, target: nil, action: nil)
        let doneButton = UIBarButtonItem(barButtonSystemItem:
            UIBarButtonItem.SystemItem.done, target: self, action: #selector(self.donePressed) )
         
        keyboardToolBar.setItems([flexibleSpace, doneButton], animated: true)
         
        self.inputAccessoryView = keyboardToolBar
    }
    
    @objc private func donePressed() {
        self.endEditing(true)
    }
}