The object is always unity and the mouse position on the z-axis position specified camera

using UnityEngine;

public class Test:MonoBehaviour{
    public Camera camera;

    private void Update(){
        var pos=Input.mousePosition;
        pos.z=-camera.transform.position.z;//减去相机的z,转换为的世界坐标z是0
        pos.z+=camera.transform.position.z+10;//放置相机前10的位置
        pos=camera.ScreenToWorldPoint(pos);
        transform.position=pos;
    }
}