title: VSCode import "C" fails on modules
body: <p>Please see the following screenshot:</p>
  
  <p><a href="https://i.stack.imgur.com/qipkI.png" rel="noreferrer"><img src="https://i.stack.imgur.com/qipkI.png" alt="vscode with golang import &quot;C&quot; error"></a></p>
  
  <p>It says:</p>
  
  <blockquote>
    <p>could not import C (no package data for import path C)</p>
  </blockquote>
  
  <p>I have attached an example project that reproduces the failure, here: <a href="https://github.com/microsoft/vscode/files/3783446/example-project.zip" rel="noreferrer">https://github.com/microsoft/vscode/files/3783446/example-project.zip</a></p>
  
  <p>I am using Go 1.13 with the latest versions of each extension for Go and C/C++.
  There is no compiler error, and this is specifically seemingly isolated as a "vscode problem".</p>
  
  <p>Is there a way to fix this vscode problem? </p>