Go Godep使用失败

I've created a basic hello-world project which works fine. I now want to use godep, so I've added it to my project using go get github.com/tools/godep, which adds the godep to my src\github.com\tools folder. now when I run godep save command (no matter where I run it - either in the 'src' folder or inside the 'godep' folder itself) I get an error - 'godep' is not recognized as an internal or external command, operable program or batch file.

I have environment variables set to -

GOPATH = C:\Users\XXX\Documents\Go\helloWorld
GOROOT = C:\Go\

and the PATH includes C:\Go\bin and according to this I've also added GOBIN = C:\Go\bin However, I still get that error message.

what did I miss?