Express GraphQl

Question

我正在尝试学习GraphQl。我没有发现任何好的课程女巫会帮助我学习它。因此，我几乎没有例子开始构建它。在这一刻，当我尝试打开http://127.0.0.0.1:3000/graphql时，我会遇到错误。它告诉我“消息”：“必须提供查询字符串。”

我认为我的用户查询做错了什么？ 这是我的完整代码。有人可以帮忙...

// user type
const UserType = new GraphQLObjectType({
  name: "User",
  description: "User Type",
  fields: () => ({
    id: { type: GraphQLInt },
    firstname: { type: GraphQLString },
    lastname: { type: GraphQLString },
    email: { type: GraphQLString },
    password: { type: GraphQLString },
  }),
});

// register (mutation)
const register = {
  type: UserType,
  args: {
    firstname: { type: GraphQLString },
    lastname: { type: GraphQLString },
    email: { type: GraphQLString },
    password: { type: GraphQLString },
  },
  //@ts-ignore
  async resolve(parent, args) {
    const { firstname, lastname, email, password } = args;

    const user = new User();
    user.firstname = firstname;
    user.lastname = lastname;
    user.email = email;
    user.password = password;
    const result = await user.save();
    console.log(result);
    return result;
  },
};

// users (query)
const users = {
  // type: new GraphQLList(UserType),
  type: UserType,
  args: { id: { type: GraphQLInt } },
  //@ts-ignore
  async resolve(parent, args) {
    const users = await User.find();
    return users;
  },
};

const MutationType = new GraphQLObjectType({
  name: "MutationType",
  description: "Mutations",
  fields: { register },
});

const QueryType = new GraphQLObjectType({
  name: "QueryType",
  description: "Queries",
  fields: { users },
});

const schema = new GraphQLSchema({ query: QueryType, mutation: MutationType });

app.use(
  "/graphql",
  graphqlHTTP({
    schema,
    graphiql: true,
  })
);

我有2个问题。

1. 当我输入浏览器时：http://127.0.0.1:3000/graphql不加载。它告诉我加载...并坚持下去。
2. 当我在失眠症中尝试它时，它告诉我

{
  "errors": [
    {
      "message": "Must provide query string."
    }
  ]
}

如何修复它？