There's no such thing as "local package". The organization of packages on a disk is orthogonal to any parent/child relations of packages. The only real hierarchy formed by packages is the dependency tree, which in the general case does not reflect the directory tree.
Just use
import "myproject/packageN"
and don't fight the build system for no good reason. Saving a dozen of characters per import in any non trivial program is not a good reason, because, for example, projects with relative import paths are not go-gettable.
The concept of import paths have some important properties:
All of the above is ruined by using relative import paths. Do not do it.
PS: There are few places in the legacy code in Go compiler tests which use relative imports. ATM, this is the only reason why relative imports are supported at all.