That's not true; it's sleeping while the thread pool is busy doing requests - analyze the code again:)
it's fine, we all went thru these gauntlets, but, if you're interested in learning more, take all of this feedback in good faith, and compare/contrast what your tool is doing vs. what sound/valid load testing tools like vegeta and hey and (maybe) k6 do. (but definitely not ab or wrk, which are unsound)