The type "task" exist in both Unity.Tasks and mscorelib

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 [here][1]. 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 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' I haven't done anything else in the project, just imported. I have no idea what to do pls help [1]: https://github.com/googlesamples/google-signin-unity/releases