Error getDataFolder () in config

Hey, I have a problem When I run My code(bottom this message) Idea: I want to create a lang.yml for Player can change The language of Plugin.

PHP:

class loader extends command {
public function execute(CommandSender $args, $command, array $args){
$cfg= new Config($this->getDataFolder() . "lang.yml", Config::YAML);
$cfg->set("lang", "en");
$cfg->save();
#Some codes not important


Console return error getDataFolder ()
Sorry for my bad english

STOP
GO TO THE NEW FORUMS

https://forums.pmmp.gq

you need to check if the dir exist if not mkdir it
often times it should be placed in the onEnable part

just dont come here eventually more people do that it would just be me helping everyone