all: update go directive to be at least 1.18 in all golang.org/x modules

[neild]

The Go version in the go.mod for x/net, x/crypto, x/text, and other x/ repos is currently go1.17, which prevents use of generics or any.

The oldest Go version within the support window is 1.19.

Is it time to update the x/ repos to depend on a post-generics version of Go? If so, perhaps we should also update packages in those repos to switch from interface{} to any at the same time.

[dmitshur]

I ended up doing something along these lines as part of work for #56530. Previously, some golang.org/x repos were on Go language version as old as 1.12, which missed out on module graph pruning, made go.sum very verbose, and otherwise got in the way of the automatic tagging/updating workflow from doing its job. I semi-arbitrary picked 1.18 because it was already used by a number of x repos even before I started updating more, and was enough to get some nice new features like module graph pruning, removed // +build lines, and so on.

By now, the oldest Go version within the support window is Go 1.20, but there's not much to be gained when going from 1.18 to 1.19 and 1.20—see https://go.dev/ref/mod#go-mod-file-go —so I stopped at 1.18 for now.

Since I was already working in x/net today for the release, I also mailed CL 534241 to get x/net up to the same 1.18 minimum bar. I'll take care of x/text and x/crypto too.

I did incorporate high confidence changes that are implemented in go fix into the CLs, like removing old-style "// +build" lines, but I'll leave other opportunities like interface{} to any or ioutil to io/os rewrites out of scope. I think they too can be done with tooling to some extent (see CL 527016 and CL 540221 for example).

[gopherbot]

Change https://go.dev/cl/534241 mentions this issue: all: update go directive to 1.18

[gopherbot]

Change https://go.dev/cl/534242 mentions this issue: all: update go directive to 1.18

[gopherbot]

Change https://go.dev/cl/534141 mentions this issue: all: update go directive to 1.18

[gopherbot]

Change https://go.dev/cl/534197 mentions this issue: all: update go directive to 1.18

[gopherbot]

Change https://go.dev/cl/534475 mentions this issue: all: update go directive to 1.18