Read body to completion before close

The default HTTP client's Transport may not
reuse HTTP/1.x "keep-alive" TCP connections if the Body is
not read to completion and closed.
See: https://golang.org/pkg/net/http/#Response

sling.go

@@ -3,6 +3,7 @@ package sling
 import (
 	"encoding/base64"
 	"io"
+	"io/ioutil"
 	"net/http"
 	"net/url"
 
@@ -384,6 +385,12 @@ func (s *Sling) Do(req *http.Request, successV, failureV interface{}) (*http.Res
 	// when err is nil, resp contains a non-nil resp.Body which must be closed
 	defer resp.Body.Close()
 
+	// The default HTTP client's Transport may not
+	// reuse HTTP/1.x "keep-alive" TCP connections if the Body is
+	// not read to completion and closed.
+	// See: https://golang.org/pkg/net/http/#Response
+	defer io.Copy(ioutil.Discard, resp.Body)
+
 	// Don't try to decode on 204s
 	if resp.StatusCode == http.StatusNoContent {
 		return resp, nil

sling_test.go

@@ -2,17 +2,20 @@ package sling
 
 import (
 	"bytes"
+	"context"
 	"encoding/xml"
 	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"math"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
 	"reflect"
 	"strings"
+	"sync/atomic"
 	"testing"
 )
 
@@ -890,6 +893,45 @@ func TestReceive_errorCreatingRequest(t *testing.T) {
 	}
 }
 
+func TestReuseTcpConnections(t *testing.T) {
+	var connCount int32
+
+	ln, _ := net.Listen("tcp", ":0")
+	rawURL := fmt.Sprintf("http://%s/", ln.Addr())
+
+	server := http.Server{
+		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			assertMethod(t, "GET", r)
+			fmt.Fprintf(w, `{"text": "Some text"}`)
+		}),
+		ConnState: func(conn net.Conn, state http.ConnState) {
+			if state == http.StateNew {
+				atomic.AddInt32(&connCount, 1)
+			}
+		},
+	}
+
+	go server.Serve(ln)
+
+	endpoint := New().Client(http.DefaultClient).Base(rawURL).Path("foo/").Get("get")
+
+	for i := 0; i < 10; i++ {
+		resp, err := endpoint.New().Receive(nil, nil)
+		if err != nil {
+			t.Errorf("expected nil, got %v", err)
+		}
+		if resp.StatusCode != 200 {
+			t.Errorf("expected %d, got %d", 200, resp.StatusCode)
+		}
+	}
+
+	server.Shutdown(context.Background())
+
+	if connCount != 1 {
+		t.Errorf("expected 1, got %v", atomic.LoadInt32(&connCount))
+	}
+}
+
 // Testing Utils
 
 // testServer returns an http Client, ServeMux, and Server. The client proxies