Xcode Playgrounds will fail network requests when Charles is running since ATS will fail. With an Xcode project you can update the Info.plist but Playgrounds don't have any such option. This is that option.

NetworkEnabler.swift

// When using Charles, the network requests will always fail unless you can bypass ATS.
public class NetworkEnabler: NSObject, NSURLSessionDelegate {
    public func URLSession(session: NSURLSession, didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler: (NSURLSessionAuthChallengeDisposition, NSURLCredential?) -> Void) {
        completionHandler(.UseCredential, NSURLCredential(trust: challenge.protectionSpace.serverTrust!))
    }
}

// Then later when making a request:
let enabler = NetworkEnabler()
let session = NSURLSession(configuration: NSURLSession.sharedSession().configuration, delegate: enabler, delegateQueue: nil)
session.dataTaskWithRequest(request) {data,response,error in
 // Code
 }.resume()