Apollo Federation: A valid schema couldn't be composed. The following composition errors were found: Syntax Error: Unexpected character: U+0130

I tried to use Apollo Federation and I create an user service and gateway. User service is working alone fine but Gateway is giving an error:

Error: A valid schema couldn't be composed. The following composition errors were found:
        Syntax Error: Unexpected character: U+0130.
    at IntrospectAndCompose.createSupergraphFromSubgraphList

Here is my code;

GATEWAY

import { ApolloGateway, IntrospectAndCompose } from "@apollo/gateway";
import { ApolloServer } from "@apollo/server";
import { expressMiddleware } from "@apollo/server/express4";
import { ApolloServerPluginDrainHttpServer } from "@apollo/server/plugin/drainHttpServer";
import express from "express";
import http from "http";
import { json } from "body-parser";

const startServer = async () => {


  const gateway = new ApolloGateway({
    supergraphSdl: new IntrospectAndCompose({
      subgraphs: [
        { name: "userService", url: "http://localhost:4001" }
      ],
    }),
  });

  const app = express();
  const httpServer = http.createServer(app);

  const server = new ApolloServer({
    gateway,
    plugins: [ApolloServerPluginDrainHttpServer({ httpServer })],
  });

  await server.start();

  await new Promise<void>((resolve) =>
    httpServer.listen({ port: 4000 }, resolve)
  );
  console.log(`🚀 Server ready at http://localhost:4000/graphql`);
};

startServer();

USER SERVICE

index.ts

import { ApolloServer } from "@apollo/server";
import { buildSubgraphSchema } from "@apollo/subgraph";
import gql from "graphql-tag";
import { resolvers } from "./graphql/resolver";
import { startStandaloneServer } from "@apollo/server/standalone";
import { readFileSync } from "fs";
const mongoose = require("mongoose");
const typeDefs = gql(
  readFileSync("src/graphql/types/user.graphql", { encoding: "utf-8" })
);

import { DB_URI } from "../database-config";

require("dotenv").config();

const createDatabaseConnection = async () => {
  try {
    await mongoose.connect(DB_URI);
    console.log("User Service: Connected to DB");
  } catch (error) {
    console.log(error);
  }
};

const startUserServiceServer = async () => {
  const server = new ApolloServer({
    schema: buildSubgraphSchema({ typeDefs, resolvers }),
  });

  await createDatabaseConnection();

  const { url } = await startStandaloneServer(server, {
    listen: { port: 4001 },
  });

  console.log(`User Service: Server ready at ${url}`);
};

startUserServiceServer();

user.graphql

extend schema
  @link(url: "https://specs.apollo.dev/federation/v2.0", import: ["@key"])

type Query {
  me: User
}

type Mutation {
  addUser(fields: UserInput): User
  updateUser(fields: UserInput): User
}

type User @key(fields: "id") {
  id: ID
  fullName: String
  phone: String
  avatarURL: String
  password: String
  email: String
  address: String
  createdAt: String
  updatedAt: String
}

input UserInput { 
  id: ID
  fullName: String
  phone: String
  avatarURL: String
  password: String
  email: String
  address: String
}

I tried to change encoding style of user.graphl as utf16lebut it didn't work. Also I use Turkish as a default language on my computer. When I switched to English the problem was gone but I couldn't understand what the problem is.

The Name in GraphQL is defined to be limited to the regular expression /[_A-Za-z][_0-9A-Za-z]*/.

The Turkish captial I (U+0130 or İ) does not match this regular expression and is considered invalid.

[source: GraphQL Spec]