Can not jump to GOROOT source in go1.4

[GoogleCodeExporter]

What steps will reproduce the problem?
1.  install go 1.4 with homebrew or compile it from source code
2.  set the $GOROOT and locate it with the new install go soruce,
3.  write a go file with code which call with std function, such as 
`json.Marshal()`
4.  trigger godef at the cursor on json.Marshal()

It should jump to the source code in GOROOT, 
but actually it does nothing.

Vsersion Info:  go version go1.4 darwin/amd64

I believe the cause is the go source code change its directory architecture, 
there are no more  $GOROOT/src/pkg.
Change the code at 
https://code.google.com/p/rog-go/source/browse/exp/cmd/godef/godef.go#49
from

            gopath = append(gopath, r+"/src/pkg")

to

    gopath = append(gopath, r+"/src")

could easy solve the problem.

Original issue reported on code.google.com by yeerku...@gmail.com on 5 Jan 2015 at 11:32