draw a straight line in swift 3 and core graphics

I'm trying to draw a single, straight line using core graphics and swift 3 However, when touchesmoved is called, it creates multiple lines instead of just a single line. Code used is below:

import UIKit

    class ViewController: UIViewController {

        @IBOutlet weak var drawingPlace: UIImageView!

        var startTouch : CGPoint?
        var secondTouch : CGPoint?

        override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
            let touch = touches.first
            startTouch = touch?.location(in: drawingPlace)
        }

        override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
            for touch in touches{
                secondTouch = touch.location(in: drawingPlace)

                UIGraphicsBeginImageContext(drawingPlace.frame.size)
                drawingPlace.image?.draw(in: CGRect(x: 0, y: 0, width: drawingPlace.frame.width, height: drawingPlace.frame.height))
                let bezier = UIBezierPath()

                bezier.move(to: startTouch!)
                bezier.addLine(to: secondTouch!)
                bezier.close()

                bezier.lineWidth = 4
                UIColor.blue.set()
                bezier.stroke()

                let img = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()
                drawingPlace.image = img   
            }
        }
    }

btw touchesEnd creates a single line but only after the user ends the touch. I want the user to see the line being drawn as they touch. thank you.