I want to make my Player Double Jump. Can anyone help me i'm stuck. :@

public class PlayerJump : MonoBehaviour {

 private float jumpForce = 10f, forwardForce = 0f;
 private Rigidbody2D myBody;
 private bool canJump;

 private bool doubleJump = false;

 private Button jumpButton;


 // Use this for initialization
 void Awake()
 {
     myBody = GetComponent<Rigidbody2D>();
     jumpButton = GameObject.Find("Jump Button").GetComponent<Button>();
     jumpButton.onClick.AddListener(() => Jump());
 }

 // Update is called once per frame
 void Update()
 {

     if (Mathf.Abs(myBody.velocity.y) == 0)
     {
         canJump = true;
     }
 }
 public void Jump()
 {
     if (canJump)
     {
         canJump = false;
         if (transform.position.x < 0)
         {
             forwardForce = 1f;
         }
         else
         {
             forwardForce = 0f;
         }
         myBody.velocity = new Vector2(forwardForce, jumpForce);
     }
 }

}