使用workerman作为http服务，使用download方法，下载文件只有3M

        $filename = $request->get('filename', '');
        if (!$filename) {
            throw new BusinessException('请输入文件名');
        }
        if (strpos($filename, '.zip') === false || strpos($filename, '..')) {
            throw new BusinessException('请输入合法文件名');
        }
        $path = BuildCSV::DATA_PATH . '/' . $filename;
        if (!file_exists($path)) {
            throw new BusinessException('文件不存在');
        }
        ini_set('memory_limit', '256M');
        return $this->download($path, $filename);