Golang: Getting started - "go" is not recognized as an internal or external command"
EDITED for future reference.
You set your 'GOROOT' wrong. Set it to C:\Go\
Include C:\Go\bin to your 'Path'
Aside from @Xeph's answer, just make sure if you recently installed Go that you use a fresh terminal/cmd window.
Run command "go env" and check the path for variable "gopath" that's where you should keep your project. Else where if you run go command you will get error "go is not recognized as internal or external command"