In terms of volume of contributions, for Go, Google employees are by far the most active: https://github.com/golang/go/pulse. In this graph, the 7 top contributors to the project are Google employees. The Rust pulse graph shows the same trend (https://github.com/rust-lang/rust/pulse), with the top 6 contributors being Mozillians (according to a few Google searches).
Something that noteworthy about Go is the "quality" of the team members: Google has Ken Thompson, Rob Pike and Russ Cox working full time on the language. Mozilla may have a few great developers on Rust too, but Google is very serious about Go.
I don't have any information about how financial and human resources are used by Google and Mozilla for the development.