title: The above error occurred in the <App> component: in App
body: <p>I started the Knowthen Go/React tutorial and I've some problem with React.
  When i try to launch my app, i've got this <a href="https://i.stack.imgur.com/WHad5.png" rel="nofollow noreferrer">error</a> and i can't figure out why.
  Here's my github repo with all my sources: <a href="https://github.com/LaLauque/RealTImePlatform/tree/dev" rel="nofollow noreferrer">https://github.com/LaLauque/RealTImePlatform/tree/dev</a></p>
  
  <p>Thanks a lot</p>