Use Shared Preferences

val user = Gson().toJson(it)
val mPrefs: SharedPreferences = requireContext().getSharedPreferences(
    SHARED_USER_PREF,
    MODE_PRIVATE)

with(mPrefs.edit()){
    putString(CURRENT_USER,user)
        .apply()} 

val pref = application.baseContext.getSharedPreferences(SHARED_USER_PREF,Context.MODE_PRIVATE)
val data = pref.getString(CURRENT_USER,null)
if (data!= null){
    val userData:User? = Gson().fromJson(data,User::class.java)
    _currentUser.value = userData
}