Why would one want to learn Go?
Overall, the language is well thought out and fixes pretty much all the issues I encountered with other languages. It is a good general purpose language with really good support for server side programming.
What types of programs does one build with Go (web, cli, etc.)?
There is a way to build pretty much everything in Go. Heck there is a GTK support as well mattn.github.io/go-gtk.
The best use-case is for writing micro-services.
What makes Go a better language than say another language like Haskell, Python, Lua, Clojure, etc?
Thats a loaded question. :)
I will try to answer in short. It would be better if you cross check it by actually writing something and comparing.
Haskel = simplicity & performance
Python = performance
Lua = I am not sure I have never used Lua at any scale :P
Clojure = slight advantage due to being compiled,
lisp vs go formats
Choosing one over other often is not an opinionated discussion, instead it is factual (in most cases). There are some languages which beats others when it comes to specific use-case and hence is irreplaceable (Yes you Erlang ). Go has its own advantages and places where it is unbeatable (networking & micro-services), just choose whichever you need based on requirement.