Sets request's GetBody field on wrapper

This commit addresses two key issues:
- Upon receiving a temporary redirect, net/http will only preserve the request's body if GetBody() is defined.
- Upon receiving a GOAWAY frame, the client will create a new connection. We define GetBody() in order to reuse the body sent in the last stream on the now terminated connection.

client.go

@@ -160,6 +160,20 @@ func (r *Request) SetBody(rawBody interface{}) error {
 	}
 	r.body = bodyReader
 	r.ContentLength = contentLength
+	if bodyReader != nil {
+		r.GetBody = func() (io.ReadCloser, error) {
+			body, err := bodyReader()
+			if err != nil {
+				return nil, err
+			}
+			if rc, ok := body.(io.ReadCloser); ok {
+				return rc, nil
+			}
+			return io.NopCloser(body), nil
+		}
+	} else {
+		r.GetBody = func() (io.ReadCloser, error) { return http.NoBody, nil }
+	}
 	return nil
 }
 
@@ -302,18 +316,19 @@ func NewRequest(method, url string, rawBody interface{}) (*Request, error) {
 // The context controls the entire lifetime of a request and its response:
 // obtaining a connection, sending the request, and reading the response headers and body.
 func NewRequestWithContext(ctx context.Context, method, url string, rawBody interface{}) (*Request, error) {
-	bodyReader, contentLength, err := getBodyReaderAndContentLength(rawBody)
+	httpReq, err := http.NewRequestWithContext(ctx, method, url, nil)
 	if err != nil {
 		return nil, err
 	}
 
-	httpReq, err := http.NewRequestWithContext(ctx, method, url, nil)
-	if err != nil {
+	req := &Request{
+		Request: httpReq,
+	}
+	if err := req.SetBody(rawBody); err != nil {
 		return nil, err
 	}
-	httpReq.ContentLength = contentLength
 
-	return &Request{body: bodyReader, Request: httpReq}, nil
+	return req, nil
 }
 
 // Logger interface allows to use other loggers than

client_test.go

@@ -978,3 +978,62 @@ func TestClient_StandardClient(t *testing.T) {
 		t.Fatalf("expected %v, got %v", client, v)
 	}
 }
+
+func TestClient_RedirectWithBody(t *testing.T) {
+	var redirects int32
+	// Mock server which always responds 200.
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.RequestURI {
+		case "/redirect":
+			w.Header().Set("Location", "/target")
+			w.WriteHeader(http.StatusTemporaryRedirect)
+		case "/target":
+			atomic.AddInt32(&redirects, 1)
+			w.WriteHeader(http.StatusCreated)
+		default:
+			t.Fatalf("bad uri: %s", r.RequestURI)
+		}
+	}))
+	defer ts.Close()
+
+	client := NewClient()
+	client.RequestLogHook = func(logger Logger, req *http.Request, retryNumber int) {
+		if _, err := req.GetBody(); err != nil {
+			t.Fatalf("unexpected error with GetBody: %v", err)
+		}
+	}
+	// create a request with a body
+	req, err := NewRequest(http.MethodPost, ts.URL+"/redirect", strings.NewReader(`{"foo":"bar"}`))
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	resp.Body.Close()
+
+	if resp.StatusCode != http.StatusCreated {
+		t.Fatalf("expected status code 201, got: %d", resp.StatusCode)
+	}
+
+	// now one without a body
+	if err := req.SetBody(nil); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	resp, err = client.Do(req)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	resp.Body.Close()
+
+	if resp.StatusCode != http.StatusCreated {
+		t.Fatalf("expected status code 201, got: %d", resp.StatusCode)
+	}
+
+	if atomic.LoadInt32(&redirects) != 2 {
+		t.Fatalf("Expected the client to be redirected 2 times, got: %d", atomic.LoadInt32(&redirects))
+	}
+}