Based on gpsoauth by Simon Weber.
With this library you can log in using username and password.
You can link the library in your dependencies manager by following instructions on https://jitpack.io/#svarzee/gpsoauth-java.
Simplest usage:
AuthToken token = new Gpsoauth().login("username", "password", "androidId", "service", "app", "clientSig");
It seems google is very strict about SSL communication and any changes to it make it fail.
It is recommended to use Gpsoauth.compatibleOkHttpClient to create OkHttpClient instance with proper SSL settings.
Using jdk other than hotspot 1.8.0_231 or openjdk 1.8.0_212 may introduce SSL implementation problems.
Using okhttp other than 3.4.1. 3.5.0, 3.6.0 may introduce SSL implementation problems.