I would recommend keeping things simple. One way to do this is to just poll periodically and check for some user input, if some key like CTL-Z has been hit, then do the command.

The terminal starts out by default in the "Enter sends line", the "cooked" or canonical mode. This mode is nice as your program doesn't have to fiddle with any user editing of the line, etc. To get raw characters (like what vi does), you need "raw" or "non-canonical" mode. If you want to read a character if one is there, else keep going, you need non-blocking mode. The Term:ReadKey module has what you need.

I would shy away from redefining CTL-C or other common control characters. This "it doesn't do what it normally would do" stuff can be a hassle and cause user confusion. I would try to pick some other key combinations that make sense to the application.

While the use of signals is possible (and there are some "user defined" ones), this doesn't sound ideal. A polling solution works great as long as you poll often enough.

Were you hung up because of not knowing how to use non-blocking and/or raw terminal mode? Or is there some other reason that polling doesn't work?

The handling of signals that can occur asynchronously while your program is at any random point adds a significant layer of complexity. I would not head in that direction unless you really need to.