This is a bare minimum Ray casting implementation in Go.
Ray casting code is only ~50 lines of code. Rest of the code is for loading map, initializing SDL etc.
There is basic input handling and no collision detection. Map is a simple text file.
You can create a Wolfenstein 3D like game with ray casting. You should add features like simple texture mapping, a pair of hands holding gun, some enemy sprites and so on.
Here is a great tutorial about ray casting.