@Test
    public void test_json_bigint_0() throws Exception {
        String str = "{\"id\":123}";
        Object id = JSONReader.of(str
                        .toCharArray())
                .readObject()
                .get("id");

        assertEquals(123, id);
    }
This mask is used to obtain the value of an int as if it were unsigned.
core/src/test/java/com/alibaba/fastjson2/read/BigIntTest.java