Clojure core.async, any way to control number of threads in that (go...) thread pool?

Clojure core.async, any way to control number of threads in that (go...)
thread pool?

By default (go..) will use 2+ number of cores threads for the thread pool.
Is there any way I can set the number of threads, or number of CPUs that
the code can use, through setting an environment variable or sth?
On linux machine I can set number of CPU using taskset, e.g. taskset -c
0,1 my_Java_or_Clojure_program, although taskset seems not effective on
the number returned by (-> (java.lang.Runtime/getRuntime)
.availableProcessors).