I'm a Vim user, and using ctags with it help me quickly navigate through code. ctags does not come with support for Go (yet?). But it's easy to add new language support to it using custom regular expressions. The below code will detect function definition in Go files. Then after running ctags -R in your project root you can hit CTRL-[ in Vim to jump to function definition.
Add the following to ~/.ctags:
Oh, and you should check out gocode as well.