Package author blub shares his package with the world, or his team, which depends on github.com/blab/blab. Unfortunately a week later github.com/blab/blab goes through a major rewrite, and breaks blub, but people doing go get blub get the new blab, and their build is broken, so they start complaining to the blub author.

Solutions to this:

Expect blab never to make a breaking change (somewhat optimistic)

Vendor a specific version of blab into blub and update manually

Explicitly specify a version of blab to use with a dependency tool

Each approach has some drawbacks.