"cannot find package" error on godoc playable examples

I'm trying to make palyable example on godoc.

• OS X Yosemite 10.10.5
• Go: go1.7.4 darwin/amd64

test code:
$GOPATH/src/hoge/hoge_test.go

package hoge_test

import (
	"fmt"
	"hoge"
	"testing"
)

func ExampleHoge() {
	fmt.Println(hoge.Hoge())

	// Output:
	// hoge!!
}

The test passes:

$ go test hoge
ok  	hoge	0.011s

Godoc

$ godoc -play -http=:8080

I can see the hoge package's example playground as I expected on a web browser, but an error below occurs when I 'Run' the example.

tmp/sandbox389904218/main.go:5:2: cannot find package "hoge" in any of:
/usr/local/go/src/hoge (from $GOROOT)
/go/src/hoge (from $GOPATH)

I set my own GOPATH, but it's not /go as shown in the error.

What I need to run examples.

Additional

I've got a reason of the error above.
Godoc playable example redirects to play.golang.org to run the code, so the GOPATH in the error seems to be on the play.golang.org environment.

I'm still not sure how to run my own pkg example though...

This is because godoc uses the golang.org/x/tools/playground tool, which just proxies requests to golang.org. It does not appear that you can run your example functions unless they are in a package that is published on golang.org. Here's the relevant file in github: https://github.com/golang/tools/blob/master/playground/common.go which is referenced by the godoc tool here: https://github.com/golang/tools/blob/master/cmd/godoc/play.go