iOS NSJSON Returning Null

I have the following code

hostStr = [hostStr stringByAppendingString:post];

NSData *dataURL =  [NSData dataWithContentsOfURL: [ NSURL URLWithString: hostStr ]];    

NSString *serverOutput = [[NSString alloc] initWithData:dataURL encoding: NSASCIIStringEncoding];    



NSError *error = nil;

NSDictionary *result = [NSJSONSerialization 

                        JSONObjectWithData:dataURL

                        options:kNilOptions 

                        error:&error];



NSArray *files = [result objectForKey:@"GV_Return"];



NSLog(@"Files: %@", files);



// For Each Key we seperate the data and add it to an object to be used.

for (NSDictionary *file in files)

{           

NSString *userNumber = [result objectForKey:@"UserNumber"];

NSLog(@"output: %@", userNumber);

}