src/Middleware.php
static function fetch(string $name) : ?callable {
        if (!isset(self::$_middleware[$name])) {
            Console::warning("Failed to fetch middleware \"$name\". Not exist.");
            return null;
        }
        return self::$_middleware[$name];
    }
static function fetch(string $name) : ?callable {
        if (!isset(self::$_middleware[$name])) {
            Console::warning("Failed to fetch middleware \"$name\". Not exist.");
            return null;
        }
        return self::$_middleware[$name];
    }
获取中间件

@param string $name
@return callable|null