How can I retrive UUID from MySQL in my Flutter app?

Question

I have a mysql table like this:

CREATE TABLE IF NOT EXISTS auth (
  id BINARY(16) PRIMARY KEY);

And create a binary UUID like following within my NodeJS application:

user_id = id: <Buffer 11 ed cd 15 15 37 82 00 bf fe a5 5d 53 c7 95 d9>

Then use an insert statement to put the new user inside the table and sign a json web token as follows:

  const jwt = jwt.sign(
    {user_id : user_id},
    process.env.JWT_KEY!,
    {
      expiresIn: process.env.JWT_EXPIRES_IN,
    }
  );

But at the front end when I try to extract user_id from the given token using the following code:

  final responseData = json.decode(response.body);
  if (responseData['error'] != null) {
    throw HttpException(responseData['error']['message']);
  }
  _token = responseData['token'];
  Map<String, dynamic> decodedToken = JwtDecoder.decode(_token!);

I see something like below when I print out decodedToken:

 {type: Buffer, data: [17, 237, 205, 21, 21, 55, 130, 0, 191, 254, 165, 93, 83, 199, 149, 217]}

Why this happens and how can I fix it?