The generated Rust clients currently use Reqwest 0.12 and rely on the query method being available on RequestBuilder.

In Reqwest 0.13, this method is no longer available by default and requires an explicit feature flag to be enabled, as noted in the release notes:
https://github.com/seanmonstar/reqwest/releases/tag/v0.13.0

I think it would be nice if the generated clients were updated to use Reqwest 0.13 with the required feature enabled out of the box.