如何指定我自己的Phoenix Channel JSON序列化程序？

defmodule MyApp.MyJSONSerializer do
  @behaviour Phoenix.Socket.JSONSerializer

  def encode(%{__struct__: struct} = data, opts) do
    # 自定义JSON序列化逻辑
    # ...
  end

  def decode(json, opts) do
    # 自定义JSON反序列化逻辑
    # ...
  end
end

config :my_app, MyApp.Endpoint,
  json_serializer: MyApp.MyJSONSerializer

defmodule MyApp.MyChannel do
  use Phoenix.Channel

  def join("room:lobby", _payload, socket) do
    {:ok, socket_assigns} = socket_assigns(socket, json_serializer: MyApp.MyJSONSerializer)
    {:ok, socket_assigns}
  end

  # ...
end