尝试连接graphql到postgress如何定义user和pass？

type User {
  id: ID!
  username: String!
  password: String!
}

type Query {
  getUser(id: ID!): User
}

type Mutation {
  createUser(username: String!, password: String!): User
}

const { ApolloServer, gql } = require('apollo-server');
const { Pool } = require('pg');

const pool = new Pool({
  user: 'your_username',
  password: 'your_password',
  host: 'your_host',
  database: 'your_database',
  port: 5432, // 默认PostgreSQL端口
});

const typeDefs = gql`
  type User {
    id: ID!
    username: String!
    password: String!
  }

  type Query {
    getUser(id: ID!): User
  }

  type Mutation {
    createUser(username: String!, password: String!): User
  }
`;

const resolvers = {
  Query: {
    getUser: async (_, { id }) => {
      const client = await pool.connect();
      try {
        const result = await client.query('SELECT * FROM users WHERE id = $1', [id]);
        return result.rows[0];
      } finally {
        client.release();
      }
    },
  },
  Mutation: {
    createUser: async (_, { username, password }) => {
      const client = await pool.connect();
      try {
        const result = await client.query('INSERT INTO users (username, password) VALUES ($1, $2) RETURNING *', [username, password]);
        return result.rows[0];
      } finally {
        client.release();
      }
    },
  },
};

const server = new ApolloServer({ typeDefs, resolvers });

server.listen().then(({ url }) => {
  console.log(`Server running at ${url}`);
});