Wait for closeFuture instead of close promise in NIOAsyncChannel's executeThenClose

Sources/NIOCore/AsyncChannel/AsyncChannel.swift

@@ -301,15 +301,13 @@ public struct NIOAsyncChannel<Inbound: Sendable, Outbound: Sendable>: Sendable {
             }
         }
 
-        do {
-            self._outbound.finish()
-            try await self.channel.close().get()
-        } catch {
-            if let error = error as? ChannelError, error == .alreadyClosed {
-                return result
-            }
-            throw error
-        }
+        self._outbound.finish()
+        // We ignore errors from close, since all we care about is that the channel has been closed
+        // at this point.
+        self.channel.close(promise: nil)
+        // `closeFuture` is never failed, so we can ignore the error
+        try? await self.channel.closeFuture.get()
+
         return result
     }
 }

Sources/NIOCore/Channel.swift

@@ -107,6 +107,11 @@ public protocol Channel: AnyObject, ChannelOutboundInvoker, _NIOPreconcurrencySe
     var allocator: ByteBufferAllocator { get }
 
     /// The `closeFuture` will fire when the `Channel` has been closed.
+    ///
+    /// - Important: This future will never be failed, as it signals when the channel has been closed, and this action cannot fail.
+    ///              If you are interested in any errors thrown during `close` to diagnose any unclean channel closures, you
+    ///              should instead use the future returned from ``Channel/close(mode:file:line:)`` or pass a promise via
+    ///              ``Channel/close(mode:promise:)``.
     var closeFuture: EventLoopFuture<Void> { get }
 
     /// The `ChannelPipeline` which handles all I/O events and requests associated with this `Channel`.