The slice returned is constructed with both a pre-set length and append() resulting in a slice twice as long and half-full of nil. Setting the capacity instead of length gets the desired result. Change-Id: I758423594e4f4c0506c53f227454f57a9dc8bdf1 Reviewed-on: https://go-review.googlesource.com/2659 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>