Module example.com/ambiguous/a is a prefix of example.com/a/b. It contains package example.com/a/b. -- .mod -- module example.com/ambiguous/a go 1.16 require example.com/ambiguous/a/b v0.0.0-empty -- .info -- {"Version":"v1.0.0"} -- go.mod -- module example.com/ambiguous/a go 1.16 require example.com/ambiguous/a/b v0.0.0-empty -- b/b.go -- package b