MyDatabase.kt

@Database(entities = [
    User::class,
    Project::class,
    Notification::class
], version = 1, exportSchema = false)
abstract class MyDatabase : RoomDatabase() {
    abstract fun users(): Users
    abstract fun projects(): Projects
    abstract fun notifications(): Notifications
     companion object {
         private var INSTANCE: MyDatabase? = null
         fun get(context: Context): MyDatabase {
            if (INSTANCE == null) {
                INSTANCE = Room.inMemoryDatabaseBuilder(context.applicationContext, MyDatabase::class.java)
                    .allowMainThreadQueries() // FIXME never do this (coroutines to come)
                    .build()
            }
            return INSTANCE!!
        }
     }
 }