The concurrency constructs (Goroutines) in Go are different and quite unique (I think D offers a number of models, but mostly pushes you towards Actors).
Go has simplicity as a much higher priority than D does.
That's assuming you care about concurrency in a low-level systems programming language. If my problem space requires concurrency I'd use clojure or erlang.
I guess if you're interested in one language for everything then maybe Go is better.
Go is not meant to be a low level systems language... it is meant to be a systems language useful for implementing services... something for which you better be caring about concurrency for.
Erlang really is the best language to point at and say "why do we need this new one", though doing that in the first place is stupid.
The concurrency constructs (Goroutines) in Go are different and quite unique (I think D offers a number of models, but mostly pushes you towards Actors).
Go has simplicity as a much higher priority than D does.
This thread might be useful: https://groups.google.com/forum/#!topic/golang-nuts/8k59Rgke...
They are both interesting languages, but you might as well say that because C++ and Ada are in GCC the rationale behind Go has gone.