proposal: cmd/go: go.mod directive allowing semver without v prefix

[prochac]

Hitting the Go module semver problem, where Go requires one and only v prefixed versions, I went through this issue and I really think that it should get some happy ending.

Some valid points, why versioning without v should be supported
#32945 (comment)
#32945 (comment)

Seems like the only reason for declining support for v-less semver tags is their collision.
#32945 (comment)
#30146 (comment)

What if the go.mod file would contain a directive that clearly declares which semver format is valid for this project?

[seankhliao]

what happens when you have a vX.Y.Z without the directive and a different X.Y.Z tag with the directive

Duplicate of #32945

[prochac]

what happens when you have a vX.Y.Z without the directive and a different X.Y.Z tag with the directive

Duplicate of #32945

For sure, the vX.Y.Z would be the default, because of the backward compatibility.

// go.mod
module module play.ground

go 1.19

versioning google // vX.Y.Z (default)
versioning semver // X.Y.Z