How to close IOS keyboard after I click "go" or "return" button in keyboard after input text in webpage.

Questions & Answers
1

How to close IOS keyboard after I click “go” or “return” button in keyboard after input text in webpage inputfield.
I don’t know how to monitor if user has clicked “go” or “return” button in unity.
How to get TouchScreenKeyboard instance except TouchScreenKeyboard.Open(…);

2 
if (Input.GetKey(KeyCode.Return) {
    touchScreenKeyboard.active = false;
}

Something like that.