title: using Kotlin with vscode on Mac --code works but intelisense shows [kotlin] Unresolved reference
body: <p>I have installed the Kotlin Language extension into vscode on Mac.
  all works fine but intelisense show errors like[kotlin] Unresolved reference: println.</p>
  
  <p>just tried with a simple .kt file :</p>
  
  <pre><code>fun main(args: Array&lt;String&gt;) {
  println("hello ,world")
  </code></pre>
  
  <p>}</p>
  
  <p>any idea what kind additional setting I should be doing ?
  thanks in advance.</p>