Since Go 1.13 (I think) it is required that a v2 release or higher contain the major version in the module directive (https://github.com/golang/go/wiki/Modules#releasing-modules-v2-or-higher).

Since this is not set, it effectively breaks updating to v2.3.0:

go get github.com/kubernetes-csi/csi-test@v2.3.0
...
require github.com/kubernetes-csi/csi-test: version "v2.3.0" invalid: module contains a go.mod file, so major version must be compatible: should be v0 or v1, not v2

The solution is rather simple, but it may be a breaking change for some users.