参考链接
苹果官网

1. 最基本的使用

/// URLSession 最基本的用法
    func baseURLSessionMethod() -> Void {
        let urlString = "http://gank.io/api/xiandu/categories"
        let url = URL(string: urlString)!
        URLSession.shared.dataTask(with: url) { (data, response, error) in
            guard error == nil else {
                NSLog("网络请求出错 -\(error.debugDescription)")
                return
            }
            guard data != nil else {
                NSLog("data 数据出错")
                return
            }
            do {
                let jsonObject = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers)
                NSLog("\(jsonObject)")
            } catch {
                NSLog("解析出错")
            }
        }.resume()
    }

2.第二种用法

func method() -> Void {
        let urlString = "http://gank.io/api/xiandu/categories"
        let url = URL(string: urlString)!
        let configure = URLSessionConfiguration.default
        let session = URLSession.init(configuration: configure)
        session.dataTask(with: url) { (data, response, error) in
            guard error == nil else {
                NSLog("网络请求出错 -\(error.debugDescription)")
                return
            }
            guard data != nil else {
                NSLog("data 数据出错")
                return
            }
            do {
                let jsonObject = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers)
                NSLog("\(jsonObject)")
            } catch {
                NSLog("解析出错")
            }
        }.resume()
    }