To change the toast notifications/message from manual closing to auto-close

[Amangnair]

As shown in screenshots above, the toast notifications/message that appears at bottom of screen when some operation has successfully completed/saved/failed, has to be closed everytime manually by clicking on the close button in the toast and if we forget to close it maually, then the toast remains idle on the screen. So, how to make it disappear automatically after sometime considering the time taken by a normal user to understand/read the message.

Can you please guide me in making required changes in respective file>code