code: func (c *Client) Notify(err error, sync bool, skip int) {
  	if c.enable {
  		c.notify(err, sync, skip)
  	}
  }
docs: // Notify takes three arguments:
  // err - standard error;
  // sync - if true then the function waits for the end of sending;
  // skip - how many errors to remove from stacktrace.