Bump go version to 1.22

[andrewsomething]

This updates to Go 1.22 following our stated Go support policy:

godo/CONTRIBUTING.md

Lines 71 to 77 in 2e0eaab

	## Go Version Support
	This project follows the support [policy of Go](https://go.dev/doc/devel/release#policy)
	as its support policy. The two latest major releases of Go are supported by the project.
	[CI workflows](.github/workflows/ci.yml) should test against both supported versions.
	[go.mod](./go.mod) should specify the oldest of the supported versions to give
	downstream users of godo flexibility.

The test changes are due to new net/http.ServeMux behavior in Go 1.22.

[loosla]

🚀