Before this change, error returned by `io.ReadFull` was silently
ignored
Signed-off-by: Michal Rostecki <mrostecki@suse.de>
Change-Id: I6a4604f0c0172a4b951fa4fc99ee83c6ba2ac8d7
Reviewed-on: https://go-review.googlesource.com/c/153137Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>