title: unity3d : The type "task" exist in both Unity.Tasks and mscorelib
body: <p>I created a blank project with unity 2019.1.4f1. I imported the firebase SDK package for authentication and another google sign in package from <a href="https://github.com/googlesamples/google-signin-unity/releases" rel="noreferrer">here</a>. I am basically trying to achieve google signin in android with firebase. But when I import the 2nd package ( google sign in), I get this error (below)</p>
  
  <p>I haven't done anything else in the project, just imported. I have no idea what to do.</p>
  
  <blockquote>
    <p>Library\PackageCache\com.unity.textmeshpro@2.0.1\Scripts\Editor\TMP_PackageUtilities.cs(310,17):
    error CS0433: The type 'Task' exists in both 'Unity.Tasks,
    Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' and 'mscorlib,
    Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'</p>
  </blockquote>