Jester relies on Nim's built-in async modules, which are unfortunately built on a single-threaded _asynchronous_ approach. This means any blocking operation done on the main thread will stall all operations.
If your aim is to pause a route, I suggest using something like [sleepAsync](http://forum.nim-lang.org///nim-lang.org/docs/asyncdispatch.html#sleepAsync,int). For operations that don't have an asynchronous version, you'll need to run the procedure on another thread.