[drtse4]

>How does it make the program run faster?

Sunfmin, wrong answer, you'd have a 20x improvement with 20 workers only with 20 cores (ignoring the limited overhead), regardless of the number of workers your queue of jobs will be consumed in number_of_jobs*single_job_duration/GOMAXPROCS.

[sunfmin]

Thanks, but there will be I/O waiting stuff right? For that whois command example, I find the CPU usage is zero if I am not running it parallel.

[drtse4]

Yup, if your jobs are i/o heavy the cpu time is wasted waiting if you execute them in a strictly sequential way. With your worker pool the cpu intensive part of the jobs is instead being executed concurrently GOMAXPROCS jobs at a time.