Thread Sleep

[BizarreCake]

I wonder why there isn't any sleep method in std.concurrency.
I know there is one in core.thread, but I try to avoid using
core modules.

Maybe a sleep method is just not needed in std.concurrency?

If I were to make a program that would constantly have about
60 working threads. Some kind of sleeping mechanism is a must
in my opinion.

Someone please answer! ^^
Thanks.