当我尝试通过apollo service:push --endpoint=http://localhost:4001将我的apollo服务器应用程序推送到Apollo引擎时，出现错误消息： Uploading service to Engine → Unknown directive "key".我在做什么错了？

我目前正在建立一个带有一堆微服务的后端项目，我想使用Apollos新的托管联合功能，其中每个微服务的graphql模式都推送到Apollo图管理器，并由apollo网关服务器进行组合。

我的模式如下：

extend type Query {
  me: User
}

type User @key(fields: "id") {
  id: ID!
  name: String
  username: String
}

这些是我的解析器：

const resolvers = {
  Query: {
    me() {
      return users[0];
    }
  },User: {
    __resolveReference(object) {
      return users.find(user => user.id === object.id);
    }
  }
};

这是我的服务器设置：

const server = new ApolloServer({
  schema: buildFederatedSchema([{ typeDefs,resolvers }])
});

server.listen({ port: 4001 }).then(({ url }) => {
  console.log(`Server ready at ${url}`);
});

apollo.config.js

module.exports = {
  service: {
    localSchemaFile: "./src/graphql/schema.graphql"
  }
};

这是完整的错误消息：

npx apollo service:push --endpoint=http://localhost:4001
  √ Loading Apollo Project
  × Uploading service to Engine
    → Unknown directive "key".
GraphQLSchemaValidationError: Unknown directive "key".
    at Object.buildSchemaFromSDL (C:/Users/Juliu/AppData/Roaming/npm-cache/_npx/13168/node_modules/apollo/node_modules/apollo-graphql/lib/schema/buildSchemaFromSDL.js:38:15)
    at FileSchemaProvider.resolveSchema (C:/Users/Juliu/AppData/Roaming/npm-cache/_npx/13168/node_modules/apollo/node_modules/apollo-language-server/lib/providers/schema/file.js:24:40)
    at GraphQLServiceProject.resolveSchema (C:/Users/Juliu/AppData/Roaming/npm-cache/_npx/13168/node_modules/apollo/node_modules/apollo-language-server/lib/project/base.js:66:36)
    at Task.task (C:/Users/Juliu/AppData/Roaming/npm-cache/_npx/13168/node_modules/apollo/lib/commands/service/push.js:70:50)