Examples: Improve the "valyala/fasthttp" example

Closes #97

(cherry picked from commit 0c70c42)

Author: erikdubbelboer

_examples/fasthttp/README.md

@@ -9,11 +9,11 @@ request and response object between `net/http` and `fasthttp`.
 To run the example:
 
     go run cmd/main.go
-    # 1000 requests in 1.15 (870.2 req/s) | min: 785.292µs / max: 10.553253ms / mean: 1.052083ms
+    # 1000 requests in 1.07 (933.4 req/s) | min: 749.961µs / max: 10.003318ms / mean: 1.013992ms
 
 To run the benchmarks:
 
     make bench
 
-    BenchmarkHTTPClient/Info()-4              2000     8721355 ns/op     16279 B/op      131 allocs/op
-    BenchmarkFastHTTPClient/Info()-4         10000     1182717 ns/op      3075 B/op       39 allocs/op
+    BenchmarkHTTPClient/Info()-4         	    1591	   7139770 ns/op	   16725 B/op	     132 allocs/op
+    BenchmarkFastHTTPClient/Info()-4     	   10000	   1315049 ns/op	    2255 B/op	      24 allocs/op

_examples/fasthttp/fasthttp.go

@@ -5,10 +5,9 @@
 package fasthttp
 
 import (
-	"bytes"
-	"io"
 	"io/ioutil"
 	"net/http"
+	"strings"
 
 	"github.com/valyala/fasthttp"
 )
@@ -22,8 +21,13 @@ type Transport struct{}
 //
 func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
 	freq := fasthttp.AcquireRequest()
+	defer fasthttp.ReleaseRequest(freq)
+
 	fres := fasthttp.AcquireResponse()
+	defer fasthttp.ReleaseResponse(fres)
+
 	t.copyRequest(freq, req)
+
 	err := fasthttp.Do(freq, fres)
 	if err != nil {
 		return nil, err
@@ -35,11 +39,9 @@ func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
 	return res, nil
 }
 
-// copyRequest converts http.Request to fasthttp.Request
+// copyRequest converts a http.Request to fasthttp.Request
 //
 func (t *Transport) copyRequest(dst *fasthttp.Request, src *http.Request) *fasthttp.Request {
-	dst.Reset()
-
 	dst.SetHost(src.Host)
 	dst.SetRequestURI(src.URL.String())
 
@@ -53,16 +55,13 @@ func (t *Transport) copyRequest(dst *fasthttp.Request, src *http.Request) *fasth
 	}
 
 	if src.Body != nil {
-		var b bytes.Buffer
-		io.Copy(&b, src.Body)
-
-		dst.SetBody(b.Bytes())
+		dst.SetBodyStream(src.Body, -1)
 	}
 
 	return dst
 }
 
-// copyResponse converts http.Response to fasthttp.Response
+// copyResponse converts a http.Response to fasthttp.Response
 //
 func (t *Transport) copyResponse(dst *http.Response, src *fasthttp.Response) *http.Response {
 	dst.StatusCode = src.StatusCode()
@@ -71,9 +70,9 @@ func (t *Transport) copyResponse(dst *http.Response, src *fasthttp.Response) *ht
 		dst.Header.Set(string(k), string(v))
 	})
 
-	if src.Body != nil {
-		dst.Body = ioutil.NopCloser(bytes.NewReader(src.Body()))
-	}
+	// Cast to a string to make a copy seeing as src.Body() won't
+	// be valid after the response is released back to the pool (fasthttp.ReleaseResponse).
+	dst.Body = ioutil.NopCloser(strings.NewReader(string(src.Body())))
 
 	return dst
 }

_examples/fasthttp/go.mod

@@ -6,5 +6,5 @@ replace github.com/elastic/go-elasticsearch/v7 => ../..
 
 require (
 	github.com/elastic/go-elasticsearch/v7 v7.0.0-20190407092644-3fb2a278216b
-	github.com/valyala/fasthttp v1.1.0
+	github.com/valyala/fasthttp v1.5.0
 )