code: public function get($key, $default = null)
      {
          if (!isset($this->data[$key])) {
              $this->data[$key] = $default;
          }
  
          $this->recordHitTimes($key);
  
          if ($this->isFirstHit($key)) {
              $this->data[$key] = $this->initService($this->data[$key]);
          }
  
          return $this->data[$key];
      }
docs: 统一 getter
  
  @param $key
  @param null $default
  @return mixed