Don't panic when failed to render or write JSON

Currently, gin will panic if failed to write JSON to client and it's
unnecessary for most scenarios. Because most of them are caused by
network error like connection reset or timeout, it'd be better to
retrieve an error instead of panic.

render/json.go

@@ -54,10 +54,7 @@ var (
 
 // Render (JSON) writes data with custom ContentType.
 func (r JSON) Render(w http.ResponseWriter) (err error) {
-	if err = WriteJSON(w, r.Data); err != nil {
+	return WriteJSON(w, r.Data)
-		panic(err)
-	}
-	return
 }
 
 // WriteContentType (JSON) writes JSON ContentType.

render/render_test.go

@@ -39,12 +39,30 @@ func TestRenderJSON(t *testing.T) {
 	assert.Equal(t, "application/json; charset=utf-8", w.Header().Get("Content-Type"))
 }
 
-func TestRenderJSONPanics(t *testing.T) {
+func TestRenderJSONFail(t *testing.T) {
 	w := httptest.NewRecorder()
 	data := make(chan int)
 
 	// json: unsupported type: chan int
-	assert.Panics(t, func() { assert.NoError(t, (JSON{data}).Render(w)) })
+	assert.Error(t, (JSON{data}).Render(w))
+}
+
+type mockWriter struct {
+	*httptest.ResponseRecorder
+}
+
+func (mock *mockWriter) Write(buf []byte) (int, error) {
+	return 0, errors.New("mock write error")
+}
+
+func TestRenderJSONWriteFail(t *testing.T) {
+	w := &mockWriter{
+		ResponseRecorder: httptest.NewRecorder(),
+	}
+	err := (JSON{map[string]any{
+		"foo": "bar",
+	}}).Render(w)
+	assert.Equal(t, errors.New("mock write error"), err)
 }
 
 func TestRenderIndentedJSON(t *testing.T) {