1. it is single tree
2. BUT tools will not propagate through the dependency tree downstream due to go module pruning
check this comment: https://github.com/golang/go/issues/48429#issuecomment-26184...
official docs: https://tip.golang.org/doc/modules/managing-dependencies#too...
> Due to module pruning, when you depend on a module that itself has a tool dependency, requirements that exist just to satisfy that tool dependency do not usually become requirements of your module.