[iOS9] NSURLSession does not work?

Hi,

I have a problem with this code

@interface NSString(urlPost)
-(NSString*) post:(NSString *)poststr;
@end

@implementation NSString(urlPost)
-(NSString*) post:(NSString *)poststr
{
    NSData *postData = [poststr dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

    NSString *postLength = [NSString stringWithFormat:@"%lu", (unsigned long)[postData length]];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];

    [request setURL:[NSURL URLWithString:self]];
    [request setHTTPMethod:@"POST"];
    [request setValue:postLength forHTTPHeaderField:@"Content-Length"];
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
    [request setHTTPBody:postData];
    [request setHTTPShouldHandleCookies:YES];

    [[NSURLSession sharedSession] downloadTaskWithRequest:request completionHandler:^(NSURL * __nullable location, NSURLResponse * __nullable response, NSError * __nullable error) {
        NSLog(@"X %@", response); //WILL NEVER BE CALLED....
    }];

    [[NSURLSession sharedSession] dataTaskWithRequest:request
                                    completionHandler:^(NSData * __nullable data, NSURLResponse * __nullable response, NSError * __nullable error)
    {
        NSLog(@"[WEB] Response Code: %@", response); //WILL NEVER BE CALLED....
    }];
}

the NSLogs will never be printed.

Other information

    NSString *test = [@"https://mysite.com:1234/CMD_LOGIN" post:@"POSTDATA=TEST"];
    NSLog(@"--> %@", test);

how to fix this?

Tanks!