Twitch batches messages that get sent (nearly) at the same time, which is why you have to split them manually. There is nothing wrong with the net module 
If that code works fine, all is well.
EDIT: I dont know exactly how net handles this, but there is a chance that long messages will arrive in parts (chunks, usually 512 bytes or something). In this case, you will have to keep a buffer of received data and split off only complete lines including \r\n. This is default handling, and if you look into the popular IRC packages, all do that.
My own code looks like this: https://gist.github.com/CBenni/4538837f6c0d5b272985