Bump go directive

[jub0bs]

The go directive remains at 1.13, and Go 1.13 dates back to 2019.

Recent versions of Go saw valuable additions, such as builtin min and max and the slices package, which would come in handy in rs/cors (try grepping the codebase for "TODO").

The go directive should be bumped to 1.22 or perhaps even 1.23. Doing so won't prevent dependents from using an older version of the library that relies on an older go directive.