refactor: Update minimum go version

[afifurrohman-id]

Currently i have make some PR that update some example using newest go version >= 1.22, but book itself is still using 1.20 as minimum version.
To do that i have add comment to every newest go example.

Maybe we need make decision a bit, about that?
Remember this is will break all content that is just work only in go 1.20 and also all examples.
I know we also need to more work, but newest go version add so much useful features, includes: http routing pattern, for range number.

How do you think @novalagung ?.