fix nil nmsg in case of empty request body

util.go

@@ -217,13 +217,21 @@ func newPathRequest(path string, method string, body string, msg interface{}, ta
 		_, _ = b.WriteString(values.Encode())
 	}
 
-	if rutil.IsZero(nmsg) {
+	if rutil.IsZero(nmsg) && !isEmptyStruct(nmsg) {
 		return b.String(), nil, nil
 	}
 
 	return b.String(), nmsg, nil
 }
 
+func isEmptyStruct(v interface{}) bool {
+	val := reflect.ValueOf(v)
+	if val.Kind() == reflect.Ptr {
+		val = val.Elem()
+	}
+	return val.Kind() == reflect.Struct && val.NumField() == 0
+}
+
 func newTemplate(path string) ([]string, error) {
 	if len(path) == 0 || path[0] != '/' {
 		return nil, fmt.Errorf("path must starts with /")

util_test.go

@@ -59,6 +59,30 @@ func TestNewPathRequest(t *testing.T) {
 	}
 }
 
+func TestNewPathRequestWithEmptyBody(t *testing.T) {
+	val := struct{}{}
+
+	for _, m := range []string{"POST", "PUT", "PATCH", "GET", "DELETE"} {
+		body := `{"type": "invalid"}`
+		path, nmsg, err := newPathRequest("/v1/test", m, body, val, []string{"protobuf", "json"}, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if nmsg == nil {
+			t.Fatalf("invalid path: nil nmsg")
+		}
+
+		u, err := url.Parse(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		vals := u.Query()
+		if len(vals) != 0 {
+			t.Fatalf("invalid path: %v nmsg: %v", path, nmsg)
+		}
+	}
+}
+
 func TestNewPathVarRequest(t *testing.T) {
 	type Message struct {
 		Name string `json:"name"`