Thank for your hard work on this. I thinking about using it for a project so giving it a thorough testing. I'm new to go so please forgive me if I've missed something obvious here. I've been coding for 20 years, but the go routines and channels are going to take a while to get my head around!

Looking at scan-syn.go, it looks like the filtered ports are never assessed or sent to the filtered channel to be added to the filtered array. Is that right?

Since we are not expecting a response, would it be right in thinking that after a timeout any port that isn't open, or closed would be essentially confirmed as filtered (unless it was just lost in the network)?