There is no modelVersion field here:
But the document says there are:
Vertex SDK also the same
The error message was made by protojson
The “modelVersion” in the response is a relatively new field, possibly available after the latest Go library update in September.
I’d open an issue on the Go library repository.
Yes, resolved after updating the library. But I am wondering if it is right that a production service is suddenly broken without any notice.