Custom http body use af 3.x

af_custom_http_body

    NSMutableURLRequest *req = [[AFHTTPRequestSerializer serializer] requestWithMethod:@"POST" URLString:@"https://example.com" parameters:@{} error:nil];
    NSString *body = @"...";
    req.HTTPBody = [body dataUsingEncoding:NSUTF8StringEncoding];
    AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] initWithSessionConfiguration:configuration];
    NSURLSessionDataTask *task = [manager dataTaskWithRequest:req completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
    }];
    
    [task resume];