title: How to make a border round out in flutter
body: <p>I need you help me. I am newbie in flutter.</p>
  <p>In flutter, I need to round out a widget, like the image below.
  <a href="https://i.stack.imgur.com/ODUeF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ODUeF.png" alt="enter image description here" /></a></p>
  <p>the red line indicate the border I want to make in flutter</p>