如何使用apollo ios客户端实现graphql订阅

我正在尝试使用apollo ios客户端实现graphql订阅.但由于缺乏文档示例而无法弄明白.
在apollo文档中给出的示例是：

let apollo: ApolloClient = {
  let configuration = URLSessionConfiguration.default
  // Add additional headers as needed
  configuration.httpAdditionalHeaders = ["Authorization": "Bearer <token>"] // Replace `<token>`

  let url = URL(string: "http://localhost:8080/graphql")!

  return ApolloClient(networkTransport: HTTPNetworkTransport(url: url, configuration: configuration))
}()

APOLLO IOS GUIDE: Creating a client

按照以下步骤在apollo ios graphql客户端中实现订阅.

>使用cocoapods：

> pod’Apollo’
> pod’Apollo / WebSocket’
> pod安装

>创建客户端以支持订阅和身份验证.在AppDelegate.swift中添加以下代码：

> Websocket – 我们必须使用WebSocketTransport和URLRequest
>身份验证 – 我们必须在连接参数connectionPayload和服务器之间传递auth参数.对于http,我们将在标题中传递它,如问题片段中所述.
> SplitNetworkTransport-结合http和websocket来创建客户端.我们必须使用httpNetworkTransport和webSocketNetworkTransport

lazy var apollo: ApolloClient = {
    let authPayloads = [
        "Authorization": "Bearer "
    ]
    let configuration = URLSessionConfiguration.default
    configuration.httpAdditionalHeaders = authPayloads

let map: GraphQLMap = authPayloads 
let wsEndpointURL = URL(string: "ws://localhost:8080/subscriptions")!
let endpointURL = URL(string: "http://localhost:8080/api")!
let websocket = WebSocketTransport(request: URLRequest(url: wsEndpointURL), connectingPayload: map)
let splitNetworkTransport = SplitNetworkTransport(
    httpNetworkTransport: HTTPNetworkTransport(
        url: endpointURL,
        configuration: configuration
    ), 
    webSocketNetworkTransport: websocket
)
return ApolloClient(networkTransport: splitNetworkTransport)

}()
let map: GraphQLMap = authPayloads 
let wsEndpointURL = URL(string: "ws://localhost:8080/subscriptions")!
let endpointURL = URL(string: "http://localhost:8080/api")!
let websocket = WebSocketTransport(request: URLRequest(url: wsEndpointURL), connectingPayload: map)
let splitNetworkTransport = SplitNetworkTransport(
    httpNetworkTransport: HTTPNetworkTransport(
        url: endpointURL,
        configuration: configuration
    ), 
    webSocketNetworkTransport: websocket
)
return ApolloClient(networkTransport: splitNetworkTransport)