I can't get my character to stop double jumping.

Hey all

For the life of me, I can't figure out how to stop my character to stop double jumping. Could you take a look at my script and let me know?

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class PlayerController : MonoBehaviour {

 public float speed;
 public float jumpForce;
 private float moveInput;

 private Rigidbody2D rb;

 private bool facingRight = true;


 private bool isGrounded;
 public Transform groundCheck;
 public float checkRadius;
 public LayerMask whatIsGround;

   
 void Start()
 {
     rb = GetComponent<Rigidbody2D>();
 }

 void FixedUpdate()
 {

     isGrounded = Physics2D.OverlapCircle(groundCheck.position, checkRadius, whatIsGround);


     moveInput = Input.GetAxis("Horizontal");
     Debug.Log(moveInput);
     rb.velocity = new Vector2(moveInput * speed, rb.velocity.y);

     if (facingRight == false && moveInput > 0)
     {
         Flip();
     }
     else if (facingRight == true && moveInput < 0)
     {
         Flip();
     }
 }

 void Update()
 {

     if (Input.GetKey("w"))
     {
         rb.velocity = Vector2.up * jumpForce;
     }
 }

 void Flip()
 {

     facingRight = !facingRight;
     Vector3 Scaler = transform.localScale;
     Scaler.x *= -1;
     transform.localScale = Scaler;
 }

}