refactor(ferry): refactore handleCommand

docs/isolates.md

@@ -61,4 +61,10 @@ If you have an authenticated graphql api and need the auth token on both the mai
    the main isolate and ferry. For example you can send the new authentication token via that sendPort. 
    The main isolate would receive it in its `messageHandler` and could persist it, for example via `SharedPreferences`. 
    You can also establish a two-way communication be creating a `ReceivePort` in the `InitClient` function and send its sendport to 
-   the main isolates messagehandler.
+   the main isolates messagehandler.
+
+Here's an example on how to wire up SharedPreferences to store
+the auth token on the main isolate, refresh it on the ferry isolate when needed, and
+send the new token the the main isolate for shared_preferences to store:
+
+https://gist.github.com/knaeckeKami/b11ad83e4b69aa44638815d1471c2ba3

examples/pokemon_explorer/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -6,7 +6,9 @@ import FlutterMacOS
 import Foundation
 
 import path_provider_macos
+import shared_preferences_macos
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
   PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
+  SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
 }

packages/ferry/lib/src/isolate/handle_command.dart

@@ -26,6 +26,7 @@ Future<void> handleCommand(TypedLinkWithCache client, IsolateCommand command,
         final stream = client.request(command.request);
         final sub = stream.doOnDone(() {
           sendPort.send(RequestResponse.done());
+          cancelEventPort.close();
         }).listen((event) {
           sendPort.send(RequestResponse.data(event));
         });