#268 Add back off to request.cancel

Author: wkh237

index.js

@@ -370,7 +370,11 @@ function fetch(...args:any):Promise {
     subscription.remove()
     subscriptionUpload.remove()
     stateEvent.remove()
-    RNFetchBlob.cancelRequest(taskId, fn)
+    // set a small backoff for insure the task already added to native task
+    // table before we cancel it.
+    setTimeout(() => {
+      RNFetchBlob.cancelRequest(taskId, fn)
+    }, 14)
   }
   promise.taskId = taskId
 

ios/RNFetchBlobNetwork.m

@@ -653,7 +653,10 @@ + (void) cancelRequest:(NSString *)taskId
 {
     NSURLSessionDataTask * task = [taskTable objectForKey:taskId];
     if(task != nil && task.state == NSURLSessionTaskStateRunning)
+    {
         [task cancel];
+        [taskTable removeObjectForKey:taskId];
+    }
 }