I've been searching Google up and down, but I can't find any documentations on Modules and how to write them.
So, My question is, how do you write Modules in Go?
The word module has many different meanings. What is your definition?
Take a look at Go packages. Read How to Write Go Code. Read the Go package documentation. Since Go is open source, look at the Go package source code for examples.
screencast on writing Go packages: http://www.youtube.com/watch?v=jDWBJOXs_iI