Add onClose method to SseClient

avaje-jex/src/main/java/io/avaje/jex/http/sse/SseClient.java

@@ -41,6 +41,14 @@ static ExchangeHandler handler(Consumer<SseClient> consumer) {
    */
   void keepAlive();
 
+  /**
+   * Add a callback that will be called either when connection is closed through {@link #close()},
+   * or when the {@link Emitter} is detected as closed.
+   *
+   * @param task task to run
+   */
+  void onClose(Runnable task);
+
   /**
    * Attempt to send a comment. If the {@link Emitter} fails to emit (remote client has
    * disconnected), the {@link #close()} function will be called instead.

avaje-jex/src/main/java/io/avaje/jex/http/sse/SseClientImpl.java

@@ -20,16 +20,24 @@ final class SseClientImpl implements SseClient {
   private final JsonService jsonService;
   private final Context ctx;
   private CompletableFuture<?> blockingFuture;
+  private Runnable closeCallback = () -> {};
 
   SseClientImpl(Context ctx) {
     this.emitter = new Emitter(ctx.exchange().getResponseBody());
     jsonService = ctx.jsonService();
     this.ctx = ctx;
   }
 
+  @Override
+  public void onClose(Runnable task) {
+    this.closeCallback = task;
+  }
+
   @Override
   public void close() {
-    if (terminated.getAndSet(true) && blockingFuture != null) {
+    if (terminated.getAndSet(true)) return;
+    closeCallback.run();
+    if (blockingFuture != null) {
       blockingFuture.complete(null);
     }
   }