I want to override theme node.tpl.php file with node--[content-type].tpl.php in my custom module I am making a new custom module. and i have 1 content type called city management(city-management).
I want to override theme node.tpl.php file with node--city-management.tpl.php in my custom module.

Is it possible?
This can be done by providing Drupal with a content type template suggestion through hook_theme. It uses the same 'node--contentname' formalism you are used to in theme templates. This method is IMHO preferred if your module also creates the content type you're theming.