@Entity(tableName = "users")
data class User(
    @PrimaryKey(autoGenerate = true)
    val id: Int? = null,

    @ColumnInfo(name = "name")
    val name: String,

    @ColumnInfo(name = "age")
    val age: Int = 0
)

@Database(entities = [User::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userDao(): UserDao

    companion object {
        private var INSTANCE: AppDatabase? = null

        fun getInstance(context: Context): AppDatabase {
            if (INSTANCE == null) {
                INSTANCE = Room.databaseBuilder(
                    context.applicationContext,
                    AppDatabase::class.java,
                    "app_database"
                ).build()
            }
            return INSTANCE as AppDatabase
        }
    }
}

@Dao
interface UserDao {
    @Insert
    suspend fun insert(user: User)

    @Query("SELECT * FROM users")
    suspend fun getAllUsers(): List<User>
}

val user = User(name = "John Doe")
AppDatabase.getInstance(this).userDao().insert(user)

val users = AppDatabase.getInstance(this).userDao().getAllUsers()
for (user in users) {
    Log.d("User", "Name: {user.name}, Age:{user.age}")
}