map[string][]string is converted to map<string, string>

[t0k4rt]

Hello,
I've got an issue with theb generated protobuf.
My function signature is
FindApp(ctx context.Context, criteria map[string][]string) ([]App, error)

The generated rpc parameter is

message appservice_FindAppRequest {
	map<string, string> arg1 = 1;
}

Is it normal ?
I tried to convert map[string][]string to a proper type like that:

type CriteriaList []string
type SearchCriteria map[string]CriteriaList

But the generated code is still the same.
I think it ois a bug but I'm not sure.
Thanks a lot for your help !