| allow_origins | string | optional | "*" | | Which Origins is allowed to enable CORS, format as：`scheme`://`host`:`port`, for example: https://somehost.com:8081. Multiple origin use `,` to split. When `allow_credential` is `false`, you can use `*` to indicate allow any origin. you also can allow all any origins forcefully using `**` even already enable `allow_credential`, but it will bring some security risks. |
| allow_methods | string | optional | "*" | | Which Method is allowed to enable CORS, such as: `GET`, `POST` etc. Multiple method use `,` to split. When `allow_credential` is `false`, you can use `*` to indicate allow all any method. You also can allow any method forcefully using `**` even already enable `allow_credential`, but it will bring some security risks. |
| allow_headers | string | optional | "*" | | Which headers are allowed to set in request when access cross-origin resource. Multiple value use `,` to split. When `allow_credential` is `false`, you can use `*` to indicate allow all request headers. You also can allow any header forcefully using `**` even already enable `allow_credential`, but it will bring some security risks. |
| expose_headers | string | optional | "*" | | Which headers are allowed to set in response when access cross-origin resource. Multiple value use `,` to split. |
| max_age | integer | optional | 5 | | Maximum number of seconds the results can be cached.. Within this time range, the browser will reuse the last check result. `-1` means no cache. Please note that the maximum value is depended on browser, please refer to [MDN](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Max-Age#Directives) for details. |
| allow_credential | boolean | optional | false | | Enable request include credential (such as Cookie etc.). According to CORS specification, if you set this option to `true`, you can not use '*' for other options. |
| allow_origins_by_regex | array | optional | nil | | Use regex expressions to match which origin is allowed to enable CORS, for example, [".*\.test.com"] can use to match all subdomain of test.com |
> Please note that `allow_credential` is a very sensitive option, so choose to enable it carefully. After set it be `true`, the default `*` of other parameters will be invalid, you must specify their values explicitly.
> When using `**`, you must fully understand that it introduces some security risks, such as CSRF, so make sure that this security level meets your expectations before using it。
