Proxy configuration is not working on Swift 5 (using Charles Proxy)

PlaygroundError.log

// The Proxy is configurated but the code isn't using it somehow.
// You can verify this by changing the kCFNetworkProxiesHTTPProxy and kCFNetworkProxiesHTTPPort values,
// and you're going to get the same output when you expect it'd fail.

url request =  Optional("https://ip.seeip.org/jsonip")
headers request =  Optional(["Accept": "application/json"])
response =  Optional(<NSHTTPURLResponse: 0x6000032aca60> { URL: https://ip.seeip.org/jsonip } { Status Code: 200, Headers {
    Connection =     (
        close
    );
    "Content-Type" =     (
        "application/json; charset=utf-8"
    );
    Date =     (
        "Tue, 10 Sep 2019 04:02:06 GMT"
    );
    Server =     (
        "openresty/1.11.2.5"
    );
    "Transfer-Encoding" =     (
        Identity
    );
} })
data body =  Optional("{\"ip\":\"172.217.162.174\"}\n")

ProxyPlayground.swift

import Foundation

class URLSessionProxy: NSObject, URLSessionDelegate {
    
    func doRequest() {
        
        let configuration = URLSessionConfiguration.default
        configuration.connectionProxyDictionary = [
            kCFNetworkProxiesHTTPEnable: true,
            kCFNetworkProxiesHTTPProxy: "localhost",
            kCFNetworkProxiesHTTPPort: "8888",
        ]
        
        var request = URLRequest(url: URL(string: "https://ip.seeip.org/jsonip")!)
        request.addValue("application/json", forHTTPHeaderField: "Accept")
    
       URLSession(configuration: configuration, delegate: self, delegateQueue: OperationQueue.main)
        .dataTask(with: request, completionHandler: { (data, response, error) in
            if error == nil {
                print("url request = ", request.url?.absoluteString)
                print("headers request = ", request.allHTTPHeaderFields.debugDescription)
                print("response = ", response)
                print("data body = ", String(data: data!, encoding: String.Encoding.utf8.self))
        
            } else {
                print("error = ", error)
                print(error?.localizedDescription)
            }
        }).resume()
    }
}

URLSessionProxy().doRequest()

terminal.log

$ curl --proxy http://localhost:8888/ https://ip.seeip.org/jsonip
{"ip":"172.217.162.174"}