title: Using Room instead singleton
body: <p>I noticed that Room lib has a Builder called <code>inMemoryDatabaseBuilder</code>, in Android Room documentation says:</p>
  
  <blockquote>
    <p>Creates a RoomDatabase.Builder for an in memory database. Information
    stored in an in memory database disappears when the process is killed.
    Once a database is built, you should keep a reference to it and re-use
    it.</p>
  </blockquote>
  
  <p>I ever used singleton to keep session object in memory and never used Room for inMemory database, my question is:
  It's a good pratic to use Room instead Singleton for storing session data in memory?
  Singleton is a bad pratic at all?
  I need in memory, because this session data are only used when the user are using the app, if the app is killed, this session data cannot persist...</p>