Big delay between getting data and setting it as UILabel Text [duplicate]

This question already has an answer here:

• UILabel text updated inside a Swift closure refuses to show 1 answer

I get currency rate using this code.

let USDAUD = NSURL(string: "http://ift.tt/1Hse127")

    let task = NSURLSession.sharedSession().dataTaskWithURL(USDAUD!) {(data, response, error) in
        println(NSString(data: data, encoding: NSUTF8StringEncoding))
        if let string = NSString(data: data, encoding: NSUTF8StringEncoding) {
            let exchangeRate = string.componentsSeparatedByString(",")[1].doubleValue
            self.displayValue.text = "\(exchangeRate)"
        }
    }

    task.resume()

But delay between getting data and setting as a label text is too high. What should i do?