init method
Implementation
Future<void> init(List<String>? allEnvKeys, List<ServerEnvConfig>? allConfigs) async {
_allEnvKeys = allEnvKeys;
_allConfigs = allConfigs;
_spf = await SharedPreferences.getInstance();
int index = _spf.getInt(KEY_SERVER_INDEX) ?? 0;
_config = _loadConfig(index);
return Future.value();
}