Tangential, but koa-router isn't even that great, been using koa-tree-router [0] instead. Fewer dependencies, no API oddities and long-standing bugs [1], faster. It's much younger (less battle-testing), and has no regex and multi-parameter routes, but is worth considering.

[0] https://github.com/steambap/koa-tree-router

[1] https://github.com/ZijianHe/koa-router/issues?q=is%3Aissue+i...