Repository with simple cache in Kotlin - caching

Question

I'm trying to implement a simple caching of a logged in user in a repository which is linked to a room database.
Here is the code of the repository
#Singleton
class UserRepository #Inject constructor(
private val webservice: Webservice,
private val userDao: UserDao
) {
var user: User? = null //simple cache of a currently logged in user
private set
init {
user = null
}
fun getUser(userId: Int): LiveData<User> {
if (user != null)
return MutableLiveData<User>(user)
val data = userDao.load(userId)
//the value is always null because the load function is done async
user = data.value
return data
}
}
And here is the UserDao
#Dao
interface UserDao {
#Query("select * from user where id = :userId")
fun load(userId: Int): LiveData<User>
}
User data is feched by a ViewModel like so
class HomeViewModel #Inject constructor(
repository: UserRepository
) : ViewModel() {
val userId: Int = MainActivity.uid
val user: LiveData<User> = repository.getUser(userId)
}
The data is fetched from the database and displayed correctly but the loaded user is never asigned to the cache because the loading is done async. Is it possible to add some listener to the load function?
I'm quite new to kotlin and android in general so if there are some better solutions for this kind of simple cache please advise.