Fixed bug:

When the connection fails, responsePromise get's deallocated (deinit is called) without being fulfilled.
This causes a fatal error in debug: "fatalError("leaking promise created at \(creation)", file: creation.file, line: creation.line)", file EventLoopFuture.swift.
The case is that when flatMap fails, there's no path in which the promise get's fulfilled.
This solution fulfills the promise, even if nothing is done with it.

Author: Eduardo Perez

Sources/NIOAPNS/APNSConnection.swift

@@ -80,10 +80,12 @@ public final class APNSConnection {
             request: buffer,
             responsePromise: responsePromise
         )
+
         return streamPromise.futureResult.flatMap { stream in
-            stream.writeAndFlush(context)
-        }.flatMap {
-            responsePromise.futureResult
+            responsePromise.futureResult.whenComplete { _ in }
+            return stream.writeAndFlush(context)
+            }.flatMap {
+                responsePromise.futureResult
         }
     }