> status.icu will return whatever https status code you want! Use a GET request to any status.icu path to guarantee an HTTP status code.

    $ curl -I https://status.icu/418/
    HTTP/1.1 500 Internal Server Error 

The Nginx configuration responsible for the service[1] just hardcodes a handful of common HTTP status codes. A Go version that supports any status code takes fewer lines than status.icu's nginx.conf, even after gofmt.[2] Not that I think anyone should be relying on a third-party service for "writing browser integration tests" OR "mocking API responses".

[1] https://gist.github.com/geetotes/0ddc96f95eecab4e8aa8dd53bcc...

[2] https://gist.github.com/wwalexander/febbc1ba76c8eafa9f94f5cb...