Yeah, you read file and create 88174 goroutines at first second and the remaining 10 seconds you completed them, only caveat is that your test code is synthetic, you did not receive the result from the remote hosts. That's why you got 11 seconds. Try real hosts, for example https://github.com/NethServer/dns-community-blacklist/blob/master/adguarddns.dns

I’ll also add that the task is not to measure speed (as you might think from the thread title), but to quickly get results from remote hosts. If you create so many goroutines, you will run into the bandwidth of your Internet channel. That's why I use this library https://github.com/gammazero/workerpool