title: Could not find an option named "web-server-debug-protocol" when running a Flutter project through VSCode
body: <p>I am using VSCode ad my Flutter development IDE. It worked well until this afternoon. When I ran the project, <code>Could not find an option named "web-server-debug-protocol"</code>showed up. I have no idea what goes wrong.
  I googled "web-server-debug-protocol" and only found two links showed that it exists in the flutter_command.dart.
  Did anyone meet the similar problem? Any suggestions about that?
  Thanks!</p>
  
  <p><a href="https://i.stack.imgur.com/m9naT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/m9naT.png" alt="enter image description here"></a></p>
  
  <p><strong>UPDATE</strong>
  I solved this issue by upgrading my Flutter.</p>