What version of Go are you using (go version)?

go version go1.12 darwin/amd64

Does this issue reproduce with the latest release?

yes

What did you do?

Use a program that references a package that no longer exists at that location. I was importing a package that imports github.com/docker/docker/container, which imports github.com/opencontainers/runc/libcontainer/label, which does not exist here anymore.

What did you expect to see?

A helpful error telling me that the package specified by a dependency does not exist.

What did you see instead?

A confusing error from here that simply says looping trying to add package.

This is confusing for the user. We should indicate better that the package does not exist or was not found at the specified location. People are hitting this, getting confused, and wasting time, which makes them dislike go modules (and go itself by relationship).

Related issue: #30394