operator-sdk: getting error - Hit an unsupported type invalid type for invalid type

I'm trying to create go operator with operator-sdk, and do next steps:

• operator-sdk new --repo=github.com/myrepo/myoperator myoperator
• cd myoperator
• operator-sdk add api --kind=MyOperator --api-version=app.example.com/v1alpha1 --skip-generation
• operator-sdk generate k8s

On last step I get the error:

INFO[0000] Running deepcopy code-generation for Custom Resource group versions: [app:[v1alpha1], ]
F0410 09:39:08.770751    1722 deepcopy.go:885] Hit an unsupported type invalid type for invalid type, from ./pkg/apis/app/v1alpha1.MyOperator

I think that I've missed something, but can't find out what exactly... Could somebody tell me what's wrong?

Thank you

I've found the root cause - GOROOT variable should be set and point to root of go installation