Undefined array key "resolver"

[zeeshsoft]

C:\xampp\htdocs\bagisto\vendor\shetabit\visitor\src\Visitor.php :80
public function __construct(Request $request, $config)
{
$this->request = $request;
$this->config = $config;
$this->except = $config['except'];
$this->via($this->config['default'], $this->config['resolver']);
$this->setVisitor($request->user());
}