It was allocating 64k of garbage per request.

benchmark                         old ns/op     new ns/op     delta
BenchmarkServer_GetRequest-2      234445        236751        +0.98%
BenchmarkServer_PostRequest-2     284443        263019        -7.53%

benchmark                         old allocs     new allocs     delta
BenchmarkServer_GetRequest-2      25             25             +0.00%
BenchmarkServer_PostRequest-2     31             30             -3.23%

benchmark                         old bytes     new bytes     delta
BenchmarkServer_GetRequest-2      1540          1540          +0.00%
BenchmarkServer_PostRequest-2     67658         1800          -97.34%

Change-Id: I9deee0ad2fddecd65c82e40782f61da0217735fc
Reviewed-on: https://go-review.googlesource.com/20542Reviewed-by: Blake Mizerany <blake.mizerany@gmail.com>
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>