我有一个用户模型，并尝试将education字段作为json对象添加到mongoDB中，如下所示，
用户模型

education: {
    "school": String,
    "years":Number
  },

客户

//add Education section
  const updateEducation = async (e) => {
    e.preventDefault();
    await fetch(`http://localhost:5000/api/user/updateEducation`, {
      method: "PUT",
      headers: { "Content-Type": "application/JSON", token: accessToken },
      body: JSON.stringify({ userid: userid, educationSchool: educationSchool,
        educationYearText: EducationYear}),
    })
      .then((res) => res.json())
      .then((data) => {
        console.log("User education is:", data.education +""+data.educationYear);
      });
  };

服务器

const updateEducation = async (req, res) => {
  try {
    const user = await User.findOneAndUpdate(
      { _id: req.body.userid },
      {
        $set: {
          'education.school': req.body.educationSchool,
          'education.years': req.body.educationYearText,
        },
      }
    );

    if (!user) {
      res.status(404).json("user not exist");
    }

    res
      .status(200)
      .json({
        education: user.education.School,
        educationYear: user.education.years,
      });
  } catch (error) {
    res.status(500).send({ error: error.message });
  }
};

当即时消息在postmanhttp：//localhost：5000/api/user/updateEducation中命中此端点时

{
"userid":"63bbe4df75dca5aac7576e47",
"educationSchool":"Test college",
"educationYearText":"2018"
}

我得到 {"错误"："findAndModify期间计划执行器错误：：原因：无法在元素{education：}中创建字段"school"[]}"}
怎么了？