Version Not Found

github.com/vrutkovs/machine-config-operator v4.2.0-alpha.0+incompatible

The requested version v4.2.0-alpha.0+incompatible cannot be found for package github.com/vrutkovs/machine-config-operator. Go to the default version (v0.0.1-0.20190705010509-53b3a21a7fb8) instead.