Go lang multithreading through txt file

Need a simple go script that will parse through a text file of emails and send mail to each of them with multi threads specified by flags or args.

If eg 4 threads are specified, the script must parse 4 emails from text file, send mail to each email, then remove the emails from the text file.

The script doesn't need to actually send email as i can implement that after if needed. A simple simulation of it sending should suffice but up to you.

if 4 threads are selected, then max of four emails being sent should be running, only moving to next email once a thread is available after sending.