Close channel for Xcode (#4)

When the channel for `XCBBuildService` is closed, basically
current service will be stall.
By closing the channel for Xcode to let service shutdown
properly, and so Xcode can restart it when it's needed again.

Signed-off-by: Yoshimasa Niwa <niw@niw.at>

Author: niw

Sources/XCBBuildServiceProxyKit/Hybrid/HybridXCBBuildService.swift

@@ -21,7 +21,14 @@ public final class HybridXCBBuildService<RequestHandler: HybridXCBBuildServiceRe
             .channelInitializer { channel in
                 xcbBuildServiceFuture.flatMap { xcbBuildService in
                     let framingHandler = RPCPacketCodec(label: "HybridXCBBuildService(\(name))")
-                    
+
+                    // When the channel for XCBBuildService is closed, such as the process is terminated,
+                    // close the channel for Xcode as well, which allows to terminate proxy process.
+                    // Xcode then relaunch it when it's needed.
+                    _ = xcbBuildService.channel.closeFuture.flatMap {
+                        channel.close()
+                    }
+
                     return channel.pipeline.addHandlers([
                         // Bytes -> RPCPacket from Xcode
                         ByteToMessageHandler(framingHandler),