SubscriberAdapter.subscriber should be final, not volatile

Author: slandelle

Diff for: client/src/main/java/org/asynchttpclient/netty/request/body/NettyReactiveStreamsBody.java

@@ -67,7 +67,7 @@ public void write(Channel channel, NettyResponseFuture<?> future) throws IOExcep
     }
 
     private static class SubscriberAdapter implements Subscriber<ByteBuf> {
-        private volatile Subscriber<HttpContent> subscriber;
+        private final Subscriber<HttpContent> subscriber;
 
         public SubscriberAdapter(Subscriber<HttpContent> subscriber) {
             this.subscriber = subscriber;