What is the closest to ConcurrentHashMap and NavigableMap in Java?

[Jacek Furmankiewicz]

if I recall from the initial Go discussion, the Go folks were 
saying that for close to realtime SLAs the goroutine/channel 
approach may have some scalability limits...which is why they 
started recommending the RW mutex approach in the end.

Now, that was a few months ago, since then Go 1.1 (and soon 1.2) 
came out, so that may be a false statement at this time.