net/http/httputil: preallocate trailerKeys slice

To prevent slice growths with append operations.

Change-Id: Icdb745b23cc44dfaf3e16746b94c06997f814e15
Reviewed-on: https://go-review.googlesource.com/23784
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
index f8b60b6d335915f6bdbc001789572c2dcc39128f..76f23bcf9a92383160524eebd2f9f25e4cd8850f 100644 (file)
--- a/src/net/http/httputil/reverseproxy.go
+++ b/src/net/http/httputil/reverseproxy.go
@@ -221,7 +221,7 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
        // The "Trailer" header isn't included in the Transport's response,
        // at least for *http.Transport. Build it up from Trailer.
        if len(res.Trailer) > 0 {
-               var trailerKeys []string
+               trailerKeys := make([]string, 0, len(res.Trailer))
                for k := range res.Trailer {
                        trailerKeys = append(trailerKeys, k)
                }