Fix exclusive access issue

Source/SocketIO/Ack/SocketAckManager.swift

@@ -58,20 +58,20 @@ private struct SocketAck : Hashable {
     }
 }
 
-struct SocketAckManager {
+class SocketAckManager {
     private var acks = Set<SocketAck>(minimumCapacity: 1)
 
-    mutating func addAck(_ ack: Int, callback: @escaping AckCallback) {
+    func addAck(_ ack: Int, callback: @escaping AckCallback) {
         acks.insert(SocketAck(ack: ack, callback: callback))
     }
 
     /// Should be called on handle queue
-    mutating func executeAck(_ ack: Int, with items: [Any]) {
+    func executeAck(_ ack: Int, with items: [Any]) {
         acks.remove(SocketAck(ack: ack))?.callback(items)
     }
 
     /// Should be called on handle queue
-    mutating func timeoutAck(_ ack: Int) {
+    func timeoutAck(_ ack: Int) {
        acks.remove(SocketAck(ack: ack))?.callback?([SocketAckStatus.noAck.rawValue])
     }
 }

Source/SocketIO/Client/SocketIOClient.swift

@@ -75,7 +75,7 @@ open class SocketIOClient : NSObject, SocketIOClientSpec {
         }
     }
 
-    var ackHandlers = SocketAckManager()
+    let ackHandlers = SocketAckManager()
 
     private(set) var currentAck = -1
 

Tests/TestSocketIO/SocketSideEffectTest.swift

@@ -38,6 +38,19 @@ class SocketSideEffectTest: XCTestCase {
         waitForExpectations(timeout: 3, handler: nil)
     }
 
+    func testHandleAckWithAckEmit() {
+        let expect = expectation(description: "handled ack")
+        socket.emitWithAck("test").timingOut(after: 0) {data in
+            XCTAssertEqual(data[0] as? String, "hello world")
+
+            self.socket.emitWithAck("test").timingOut(after: 0) {data in}
+            expect.fulfill()
+        }
+
+        manager.parseEngineMessage("30[\"hello world\"]")
+        waitForExpectations(timeout: 3, handler: nil)
+    }
+
     func testHandleAck2() {
         let expect = expectation(description: "handled ack2")
         socket.emitWithAck("test").timingOut(after: 0) {data in