@the42 But if you were to create the vendor dir in a subdirectory, the resulting build would behave differently from vgo. Perhaps what you need is to make the command(s) their own module?

Ok, I tried the following:
package (go.mod)
\cmd\service\main.go (here I also created an empty go.mod)

(note: nested go.mod for the command within a go.mod for the package root / module root)

when I run vgo vendor inside package (module root) a vendor directory is created
when I run vgo build ... inside package (module root) the package and the cmd\service gets built

After vgo build ... the contents of package/cmd/service/go.mod becomes

module "github.com/the42/badge"

however no require directives get written. If I execute vgo build inside package/cmd/service I get the following error message:

can't load package: import cycle not allowed
package github.com/the42/badge
imports github.com/the42/badge
import cycle not allowed
package github.com/the42/badge
imports github.com/the42/badge

Also vgo vendor inside package/cmd/service fails with

vgo vendor: open /home/john/src/gocode/src/github.com/the42/badge/cmd/service/vendor/vgo.list: no such file or directory

I guess you meant to completely separate the package from the command, but that way it's no longer nicely encapsulated

I don't think we're going to do this. The module defines a set of code versions that apply to the whole modules, not to just one subdirectory. "vgo vendor" is about freezing everything for the module, not just one command. The right place for the vendor dir really is the module root, not piecemeal within the module tree.