How do I read header from Volley request's JSON response?

Question

I am developing an application where Logging In returns a cookie named "authCookie" from server and this cookie is in header of the response. I am using Volley library and String Request for server-mobile application communication. Can you please guide me how do I get this cookie from header?

    StringRequest stringRequest = new StringRequest(Request.Method.POST, URL,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) { 
                    try {
                        JSONObject obj = new JSONObject(response);
                        if(obj.has("csrf") && obj.has("refreshToken")){
                            csrf = obj.getString("csrf");
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }

            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    progressDialog.dismiss();

                    NetworkResponse networkResponse = error.networkResponse;
                    if (networkResponse != null){
                        if(error.networkResponse.statusCode == 400){
                            Toast.makeText(MainActivity.this,"Invalid username/password",Toast.LENGTH_LONG).show();
                        }
                    }
                    else{
                        Toast.makeText(MainActivity.this,"Check internet connection!",Toast.LENGTH_LONG).show();
                    }
                }
            }) {
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> params = new HashMap<>();
            params.put("username", username);
            params.put("password", password);
            return params;
        }

   };

    VolleySingleton.getInstance(this).addToRequestQueue(stringRequest);

I want authCookie from response and save it in a string.