iOS, Swift, back button

- prev ViewController
-- add

@IBAction func myExit(sender : UIStoryboardSegue){

}

- storyboard
-- add button
--- drag button to Exit(3rd icon upper menu)


ref : https://m.blog.naver.com/PostView.nhn?blogId=jdub7138&logNo=220393890771&proxyReferer=https%3A%2F%2Fwww.google.co.jp%2F