Whitley, 20, spent time on loan at South Shields last season, and made his Boro debut in the league opener against Atherton Collieries.
Manager Darren Kelly said: "Ryan is a hugely promising young goalkeeper who I know very well as myself and Michael Ingham brought him into the York City academy a number of years ago.
"He is a very good young goalkeeper who will strengthen us a great deal."
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