public function info($key)
{
$key = trim($key);
$url = "{$this->QINIU_RS_HOST}/stat/" . self::qiniuEncode("{$this->bucket}:{$key}");
$accessToken = $this->accessToken($url);
$response = $this->request($url, 'POST', ['Authorization' => "QBox {$accessToken}"]);
return $response;
}