I wanted to say Go as well, but compared to any other possibly-mainstream languages, Go is very innovative - it has fibres/goroutines, channels, and structural typing/lack of class-based inheritance!
Which raises an interesting point: what to people on the outside looks like a paradoxical combination of insane hubris and deep technical conservatism is probably simply what to Google's eyes looks like steady-state, responsible technical problem-solving -- c.f., hhvm and Facebook for a similar approach.
And Kotlin's is "compile faster than Scala"!