fix: update readme with new parameter and correct callback setter

README.md

@@ -13,7 +13,7 @@ Casbin role watcher to be used for monitoring updates to casbin policies
 pip install casbin-postgresql-watcher
 ```
 
-## Basic Usage Example 
+## Basic Usage Example
 ### With Flask-authz
 ```python
 from flask_authz import CasbinEnforcer
@@ -22,7 +22,7 @@ from flask import Flask
 from casbin.persist.adapters import FileAdapter
 
 casbin_enforcer = CasbinEnforcer(app, adapter)
-watcher = PostgresqlWatcher(host=HOST, port=PORT, user=USER, password=PASSWORD)
-watcher.set_update_callback(casbin_enforcer.e.load_policy())
+watcher = PostgresqlWatcher(host=HOST, port=PORT, user=USER, password=PASSWORD, dbname=DBNAME)
+watcher.set_update_callback(casbin_enforcer.e.load_policy)
 casbin_enforcer.set_watcher(watcher)
-```
+```