AFNetworking background task not working - ios

Question

Here is my code to post image in server with background feature but it gives error
NSURLSessionConfiguration *config = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:#"com.uploadDocument.Background"];
MBProgressHUD *progres = [MBProgressHUD showHUDAddedTo:[[AppDelegate sharedInstance] window] animated:YES];
progres.mode = MBProgressHUDModeDeterminateHorizontalBar;
progres.progress = 0.0;
if (!self.sessionManager) {
_sessionManager = [[AFHTTPSessionManager alloc] initWithSessionConfiguration:config];
}
NSError *error;
NSMutableURLRequest *requet= [[AFHTTPRequestSerializer serializer] multipartFormRequestWithMethod:#"POST" URLString:#"url_post" parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> _Nonnull formData) {
NSError *error1;
[formData appendPartWithFileURL:[NSURL fileURLWithPath:filePath] name:#"fileUpload" fileName:path mimeType:#"image/jpeg" error:&error1];
NSLog(#"%#",error1);
NSLog(#"%#",filePath);
} error:&error];
NSLog(#"%#",requet);
NSURLSessionUploadTask *uploadTask = [self.sessionManager uploadTaskWithRequest:requet fromFile:[NSURL fileURLWithPath:filePath] progress:^(NSProgress * _Nonnull uploadProgress) {
dispatch_async(dispatch_get_main_queue(), ^{
[progres setProgress:uploadProgress.fractionCompleted];
});
NSLog(#"%f",uploadProgress.fractionCompleted);
} completionHandler:^(NSURLResponse * _Nonnull response, id _Nullable responseObject, NSError * _Nullable error) {
NSLog(#"%#",response);
NSLog(#"%#",error);
dispatch_async(dispatch_get_main_queue(), ^{
[MBProgressHUD hideHUDForView:[AppDelegate sharedInstance].window animated:YES];
});
}];
[uploadTask resume];
Response Code=-1011 "Request failed: internal server error (500)" UserInfo={com.alamofire.serialization.response.error.response=
"Unexpected end of MIME multipart stream. MIME multipart message is not complete." in .NET Error
Please Help me solve that
This is working but no background config.
[self.sessionManager POST:#"URL " parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
[formData appendPartWithFileData:[NSData dataWithContentsOfFile:filePath]
name:#"fileUpload"
fileName:path mimeType:#"image/jpeg"];
} progress:^(NSProgress * uploadProgress) {
NSLog(#"%f",uploadProgress.fractionCompleted);
dispatch_async(dispatch_get_main_queue(), ^{
[progres setProgress:uploadProgress.fractionCompleted];
});
} success:^(NSURLSessionDataTask *task, id responseObject) {
NSLog(#"Response: %#", responseObject);
dispatch_async(dispatch_get_main_queue(), ^{
[MBProgressHUD hideHUDForView:[AppDelegate sharedInstance].window animated:YES];
});
} failure:^(NSURLSessionDataTask *task, NSError *error) {
NSLog(#"Error: %#", error);
dispatch_async(dispatch_get_main_queue(), ^{
[MBProgressHUD hideHUDForView:[AppDelegate sharedInstance].window animated:YES];
});
}];