I'm trying to get my player to jump when the spacebar is pressed. My character does jump, but when I hold space, it keeps going up in the air. I do know what the problem is with my code, it's just that I don't know how to fix it.

Here's my code:

```
using UnityEngine;

public class PlayerMovement : MonoBehaviour
{

    public Rigidbody rb;

    public float forwardForce = 500f;
    public float sidewaysForce = 500f;
    public float jumpForce = 200f;

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

        // Let the player have the ability to move around using wasd keys and jump using the space key
        if (Input.GetKey("w")) 
        {
            rb.AddForce(0, 0, forwardForce * Time.deltaTime);
        }

        if (Input.GetKey("a"))
        {
            rb.AddForce(-sidewaysForce * Time.deltaTime, 0,  0);
        }

        if (Input.GetKey("s")) 
        {
            rb.AddForce(0, 0, -forwardForce * Time.deltaTime);
        }

        if (Input.GetKey("d")) 
        {
            rb.AddForce(sidewaysForce * Time.deltaTime, 0, 0);
        }

        if (Input.GetKey(KeyCode.Space)) 
        {
            rb.AddForce(0, jumpForce * Time.deltaTime, 0);
        }

    }

}

```

Any suggestions would be really helpful.