Issue #60: skip body copying in DoTimeout. This should improve DoTimeout performance when dealing with big request and/or response bodies

client.go

@@ -862,7 +862,8 @@ func clientDoDeadlineFreeConn(req *Request, resp *Response, deadline time.Time,
 	// Make req and resp copies, since on timeout they no longer
 	// may be accessed.
 	reqCopy := AcquireRequest()
-	req.CopyTo(reqCopy)
+	req.copyToSkipBody(reqCopy)
+	swapRequestBody(req, reqCopy)
 	respCopy := AcquireResponse()
 
 	// Note that the request continues execution on ErrTimeout until
@@ -889,7 +890,8 @@ func clientDoDeadlineFreeConn(req *Request, resp *Response, deadline time.Time,
 	var err error
 	select {
 	case err = <-ch:
-		respCopy.CopyTo(resp)
+		respCopy.copyToSkipBody(resp)
+		swapResponseBody(resp, respCopy)
 		ReleaseResponse(respCopy)
 		ReleaseRequest(reqCopy)
 		errorChPool.Put(chv)

http.go

@@ -433,9 +433,13 @@ func (req *Request) ResetBody() {
 
 // CopyTo copies req contents to dst except of body stream.
 func (req *Request) CopyTo(dst *Request) {
+	req.copyToSkipBody(dst)
+	dst.body = append(dst.body[:0], req.body...)
+}
+
+func (req *Request) copyToSkipBody(dst *Request) {
 	dst.Reset()
 	req.Header.CopyTo(&dst.Header)
-	dst.body = append(dst.body[:0], req.body...)
 
 	req.uri.CopyTo(&dst.uri)
 	dst.parsedURI = req.parsedURI
@@ -449,12 +453,26 @@ func (req *Request) CopyTo(dst *Request) {
 
 // CopyTo copies resp contents to dst except of body stream.
 func (resp *Response) CopyTo(dst *Response) {
+	resp.copyToSkipBody(dst)
+	dst.body = append(dst.body[:0], resp.body...)
+}
+
+func (resp *Response) copyToSkipBody(dst *Response) {
 	dst.Reset()
 	resp.Header.CopyTo(&dst.Header)
-	dst.body = append(dst.body[:0], resp.body...)
 	dst.SkipBody = resp.SkipBody
 }
 
+func swapRequestBody(a, b *Request) {
+	a.body, b.body = b.body, a.body
+	a.bodyStream, b.bodyStream = b.bodyStream, a.bodyStream
+}
+
+func swapResponseBody(a, b *Response) {
+	a.body, b.body = b.body, a.body
+	a.bodyStream, b.bodyStream = b.bodyStream, a.bodyStream
+}
+
 // URI returns request URI
 func (req *Request) URI() *URI {
 	req.parseURI()