godoc: fix test failure
godoc: fix test failure

Adjust code to satisfy vet.

Change-Id: I532b4d988eb29b413520de60b8520d9e100b42c9
Reviewed-on: https://go-review.googlesource.com/118557
Run-TryBot: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools