[go1.20] tool doesn't recurse into sub-directories

[dprotaso]

Unsure why but with go1.20 the tool doesn't recurse into sub-directories anymore.

Script is invoked the following way
https://github.com/knative/eventing/blob/main/hack/update-reference-docs.sh

Output is

I0227 10:51:28.226464   96710 main.go:132] parsing go packages in directory knative.dev/eventing/pkg/apis
F0227 10:51:28.242770   96710 main.go:135] no loaded build package for knative.dev/eventing/pkg/apis
exit status 255

[dprotaso]

gengo - issue - kubernetes/gengo#241

[dprotaso]

Workaround is to place an empty go file into the empty directory so that there is always code