Thread safety

Author: johnno1962

Foundation/URLSession/URLSession.swift

@@ -405,9 +405,13 @@ extension URLSession._Request {
 }
 
 fileprivate extension URLSession {
+    static let identiferLock = NSLock()
+
     func createNextTaskIdentifier() -> Int {
+        URLSession.identiferLock.lock()
         let i = nextTaskIdentifier
         nextTaskIdentifier += 1
+        URLSession.identiferLock.unlock()
         return i
     }
 }