this file is aiming to use URLSession to make a web service api call using swift 3

DataTask.swift

//
//  DataTask.swift
//  
//
//  Created by Amr AlGhadban on 2/15/17.
//  Copyright © 2017 Amr AlGhadban. All rights reserved.
//

import Foundation

class DataTask: NSObject {


    class var sharedInstance : DataTask{
        struct Static {
            static let instance : DataTask = DataTask()
        }
        return Static.instance
    }

    private static func apiURlBuilder (_ subUrl : String?)-> String {
        return  ConstantsStruct.WebServiceAPIKey.BASEURL + subUrl!
    }
    // inoke via key=value & key=value

    public static func invokeAPI(_ urlSubString: String, parameters: String?, completionHandler:@escaping (_ status: Bool, _ object: NSDictionary?) -> Void){
        UIApplication.shared.isNetworkActivityIndicatorVisible = true
        let defaultConfigObject = URLSessionConfiguration.default
        let defaultSession = URLSession(configuration: defaultConfigObject)
        
        let url = URL(string: apiURlBuilder(urlSubString))
        var urlRequest = URLRequest(url: url!)
        urlRequest.httpMethod = "POST"
        urlRequest.httpBody = parameters?.data(using: String.Encoding.utf8)
        urlRequest.timeoutInterval = 10
        
        let task = defaultSession.dataTask(with: urlRequest, completionHandler: { data, response, error in
            guard error == nil && data != nil else {
                UIApplication.shared.isNetworkActivityIndicatorVisible = false
                completionHandler(false, nil)
                DispatchQueue.main.async(execute: {
                   // self.showAlertWithTitle("TrucksGo", message: error?.localizedDescription)
                })
                return
            }
            UIApplication.shared.isNetworkActivityIndicatorVisible = false
            
            if let httpStatus = response as? HTTPURLResponse , httpStatus.statusCode == 200 {
                do {
                    
                    //Store response in NSDictionary for easy access
                    let responseObj = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions()) as! NSDictionary
                    
                    print("*** parsed date as NSDictiornary : ",responseObj)
                    
                    if let statusCode : Int = responseObj["responseCode"] as? Int , 200...299 ~= statusCode {
                        DispatchQueue.main.async {
                            completionHandler(true, responseObj as NSDictionary)
                        }
                    } else {
                        let dataString = String(data: data!, encoding: String.Encoding(rawValue: String.Encoding.utf8.rawValue))
                        print(dataString ?? "No data")
                        
                        DispatchQueue.main.async {
                            completionHandler(false, responseObj as NSDictionary)
                        }
                    }
                } catch {
                    DispatchQueue.main.async {
                        completionHandler(false, nil)
                    }
                }
            } else {
                DispatchQueue.main.async {
                    completionHandler(false, nil)
                }
            }
        })
        task.resume()
    }


}




/*

func loadingJSON(_ link:String, postString:String, completionHandler: @escaping (_ JSONObject: AnyObject) -> ()) {
    if(isConnectedToNetwork() == false){
        completionHandler("-1" as AnyObject)
        return
    }
    
    let request = NSMutableURLRequest(url: URL(string: link)!)
    request.httpMethod = "POST"
    request.httpBody = postString.data(using: String.Encoding.utf8)
    
    let task = URLSession.shared.dataTask(with: request as URLRequest) { data, response, error in
        guard error == nil && data != nil else {                                                          // check for fundamental networking error
            print("error=\(error)")
            return
        }
        
        if let httpStatus = response as? HTTPURLResponse , httpStatus.statusCode != 200 {           // check for http errors
            print("statusCode should be 200, but is \(httpStatus.statusCode)")
            print("response = \(response)")
        }
        
        
        //JSON successfull
        do {
            
            let parseJSON = try JSONSerialization.jsonObject(with: data!, options: .allowFragments)
            
            DispatchQueue.main.async(execute: {
                completionHandler(parseJSON as AnyObject)
            });
            
            
        } catch let error as NSError {
            print("Failed to load: \(error.localizedDescription)")
            
        }
    }
    task.resume()
}


func isConnectedToNetwork() -> Bool {
    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
    zeroAddress.sin_family = sa_family_t(AF_INET)
    
    guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
        $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
            SCNetworkReachabilityCreateWithAddress(nil, $0)
        }
    }) else {
        return false
    }
    
    var flags: SCNetworkReachabilityFlags = []
    if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
        return false
    }
    
    let isReachable = flags.contains(.reachable)
    let needsConnection = flags.contains(.connectionRequired)
    
    return (isReachable && !needsConnection)
}
So now you can easily call this in your app wherever you want

loadingJSON("yourDomain.com/login.php", postString:"email=\(userEmail!)&password=\(password!)") {
    parseJSON in
    
    if(String(describing: parseJSON) == "-1"){
        print("No Internet")
    } else {
        
        if let loginSuccessfull = parseJSON["loginSuccessfull"] as? Bool {
            //... do stuff
        }
}

*/

how to use this file is by the following line for codes

           // TODO show loader 
            let params =  "mobile_no=01098558500&password=123123" 
            DataTask.invokeAPI("url/login", parameters: params, completionHandler: {(status: Bool,object: NSDictionary?) in
              // TODO close loader 
                 if (status == true){
          
                   // TODO business logic
                    
                }else{
                
                 // TODO show alert Message for error
                
                }
            })