6.2.0-beta set value issue

Created by: bestpika

This code at 6.1.0-beta is worked.

#include "ArduinoJson.h"

DynamicJsonDocument doc;
JsonObject root;

void setup() {
  Serial.begin(115200);
  Serial.print("\n\n");
  root = doc.to<JsonObject>();

  String key1 = "key1";
  auto val1 = "val1";
  root[key1] = val1;

  String key2 = "key2";
  auto val2 = 2;
  root.set(key2, val2);

  serializeJsonPretty(root, Serial);
  Serial.print("\n\n");
}

void loop() {}

But at 6.2.0-beta I get {}