$ hugo help mod get
Resolves dependencies in your current Hugo Project.
Some examples:
Install the latest version possible for a given module:
hugo mod get github.com/gohugoio/testshortcodes
Install a specific version:
hugo mod get github.com/gohugoio/testshortcodes@v0.3.0
Install the latest versions of all module dependencies:
hugo mod get -u
hugo mod get -u ./... (recursive)
So I think you can do:
$ hugo mod get github.com/owner/repo