src/Cron.php
static function instance(string $name) : ?self {
        if (!isset(self::$_instances[$name])) {
            Console::warning("Cron service \"$name\" do not exist.");
            return null;
        }
        return self::$_instances[$name];
    }
static function instance(string $name) : ?self {
        if (!isset(self::$_instances[$name])) {
            Console::warning("Cron service \"$name\" do not exist.");
            return null;
        }
        return self::$_instances[$name];
    }
获取计划任务服务实例

@param string $name
@return Cron|null