The defender moved to Paisley on transfer deadline day last October, initially on loan, but the Northern Irish under-21 cap will remain at the SMISA Stadium next season.
He made his first appearance of the season in the midweek win over Ross County and Goodwin said: “We have a contract in place and an agreement in place with Rangers that Daniel will join up with us full-time in the summer," he said.
"He's one for the future. We had that conversation with Daniel and his representatives. We explained the project we have and what we're looking for from Daniel. It was never about him coming in and getting 15 or 20 first-team games.
"We wanted him to come in and train with senior pros and compete against the likes of Jon Obika, Lee Erwin and Kristian Dennis on a daily basis so he could learn.
"He's one we're looking at as another kind of Jason Naismith type who could go on and have a very successful career."
Finlayson captained Rangers under-17s to the 2018 Glasgow Cup and Scottish Youth Cup a year later. He spent time with Rangers’ partner club Orange County before cutting his stay Stateside short to sign up with the Saints.
Rangers have several youths on loan throughout the Scottish system for experience, including Chris McKee at Brechin and Kyle McLelland at Falkirk, through to a trio at Queen of the South and Kai Kennedy at Raith as well as Stephen Kelly at Ross County and Glenn Middleton with St Johnstone.