Do function panics when HTTPClient returns a nil response (#714)

stripe.go

@@ -351,17 +351,22 @@ func (s *BackendImplementation) Do(req *http.Request, body *bytes.Buffer, v inte
 			break
 		}
 
-		resBody, err := ioutil.ReadAll(res.Body)
-		res.Body.Close()
 		if err != nil {
 			if s.LogLevel > 0 {
-				s.Logger.Printf("Cannot read response: %v\n", err)
+				s.Logger.Printf("Request failed with error: %v\n", err)
+			}
+		} else {
+			resBody, err := ioutil.ReadAll(res.Body)
+			res.Body.Close()
+			if err != nil {
+				if s.LogLevel > 0 {
+					s.Logger.Printf("Cannot read response: %v\n", err)
+				}
+			} else {
+				if s.LogLevel > 0 {
+					s.Logger.Printf("Request failed with body: %s (status: %v)\n", string(resBody), res.StatusCode)
+				}
 			}
-			return err
-		}
-
-		if s.LogLevel > 0 {
-			s.Logger.Printf("Request failed with: %s (error: %v)\n", string(resBody), err)
 		}
 
 		sleepDuration := s.sleepTime(retry)
@@ -381,6 +386,7 @@ func (s *BackendImplementation) Do(req *http.Request, body *bytes.Buffer, v inte
 		}
 		return err
 	}
+
 	defer res.Body.Close()
 
 	resBody, err := ioutil.ReadAll(res.Body)

stripe_test.go

@@ -9,10 +9,12 @@ import (
 	"regexp"
 	"runtime"
 	"sync"
+	"sync/atomic"
 	"testing"
+	"time"
 
 	assert "github.com/stretchr/testify/require"
-	stripe "github.com/stripe/stripe-go"
+	"github.com/stripe/stripe-go"
 	. "github.com/stripe/stripe-go/testing"
 )
 
@@ -118,6 +120,51 @@ func TestDo_Retry(t *testing.T) {
 	assert.Equal(t, 2, requestNum)
 }
 
+func TestDo_RetryOnTimeout(t *testing.T) {
+	type testServerResponse struct {
+		Message string `json:"message"`
+	}
+
+	timeout := time.Second
+	var counter uint32
+
+	testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		atomic.AddUint32(&counter, 1)
+		time.Sleep(timeout)
+	}))
+	defer testServer.Close()
+
+	backend := stripe.GetBackendWithConfig(
+		stripe.APIBackend,
+		&stripe.BackendConfig{
+			LogLevel:          3,
+			MaxNetworkRetries: 1,
+			URL:               testServer.URL,
+			HTTPClient:        &http.Client{Timeout: timeout},
+		},
+	).(*stripe.BackendImplementation)
+
+	backend.SetNetworkRetriesSleep(false)
+
+	request, err := backend.NewRequest(
+		http.MethodPost,
+		"/hello",
+		"sk_test_123",
+		"application/x-www-form-urlencoded",
+		nil,
+	)
+	assert.NoError(t, err)
+
+	var body = bytes.NewBufferString("foo=bar")
+	var response testServerResponse
+
+	err = backend.Do(request, body, &response)
+
+	assert.Error(t, err)
+	// timeout should not prevent retry
+	assert.Equal(t, uint32(2), atomic.LoadUint32(&counter))
+}
+
 func TestFormatURLPath(t *testing.T) {
 	assert.Equal(t, "/resources/1/subresources/2",
 		stripe.FormatURLPath("/resources/%s/subresources/%s", "1", "2"))