Looking at the GKE go sample, I see that it uses pulumi specific types for things like Strings and Arrays instead of using native go types. Is that just a case of the sample not being updated, or is that working as intended?

This is indeed as intended. The reason is due to the lack of generics in Go. Due to the async nature of the cloud, we model a given input to a cloud resource as

Input<T> = T | Output<T>

where T is your plain string type, and

Output<T>

is a future/promise that will eventually produce a T. In languages like Typescript and C#, we can use generics to represent this and allow using native types. In go we have to create this custom

pulumi.String

<http://pulumi.Int|pulumi.Int>

etc, to work around this. If you'd like a high level overview I recommend watching this: https://www.crowdcast.io/e/2020-04-14-PNW-Go or

we found the async nature in TS very hard to work with at times…

Agreed, the async nature can be a little bit of a mind bender.