Camera go through the wall, help!

Hey,

How do I stop my camera from going through the wall(collider)?

I want make a camera move left/right/forward/back/up/down just like a bird.

I try to do it,but still a problem that the camera go through the collider.

I search the question in the fourm,but have not sloved it.

I add CharacterController script to the camera and use character motor to control it.

When I go up it will fall down,I don't want it.

So I use the RayCast.When I go forward ,it work well.But the other direction also go through collider.

 using UnityEngine;
 using System.Collections;
 
 public class MyFreeFlyCamera : MonoBehaviour {
     public float speed = 10;
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
         RaycastHit hitInfo;
         Vector3 fwd = transform.TransformDirection(Vector3.forward);
         if (Physics.Raycast(transform.position, fwd, out hitInfo, 1))
         {
             print("There is something in front of the object!");
             float dis = hitInfo.distance;
             Vector3 correction = Vector3.Normalize(transform.TransformDirection(Vector3.back)) * dis*Time.deltaTime;
             transform.position = transform.position + correction;
             return;
         }
 
 
         if (Input.GetKey(KeyCode.W))
         {
             gameObject.transform.Translate(Vector3.forward * Time.deltaTime * speed);
         }
 
         if (Input.GetKey(KeyCode.S))
         {
             gameObject.transform.Translate(Vector3.back * Time.deltaTime * speed);
         }
 
         if (Input.GetKey(KeyCode.A))
         {
             gameObject.transform.Translate(Vector3.left * Time.deltaTime * speed);
         }
 
         if (Input.GetKey(KeyCode.D))
         {
             gameObject.transform.Translate(Vector3.right * Time.deltaTime * speed);
         }
 
         if (Input.GetKey(KeyCode.UpArrow))
         {
             gameObject.transform.Translate(Vector3.up * Time.deltaTime * speed);
         }
 
         if (Input.GetKey(KeyCode.DownArrow))
         {
             gameObject.transform.Translate(Vector3.down * Time.deltaTime * speed);
         }
     }
 
 }

Could anyone help?Thank you very much.