I need to call an OPC UA method with a struct as an InputArgument. In this case, the struct is a AnonymousIdentityToken. I tried to create an ExtensionObject containing the tokenValue, but this was not successful when the method was called.

token := ua.AnonymousIdentityToken{PolicyId: "anonymous"}
myVariant := ua.MustVariant(???)

req := &ua.CallMethodRequest{
        ObjectID:       ua.NewStringNodeID(2, "main"),
        MethodID:       ua.NewStringNodeID(2, "even"),
        InputArguments: []*ua.Variant{
                        myVariant,
                        ... more inputArguments...
                        },
    }

So how can a structured value be passed into a Variant?