Johnson, 32, appeared in 36 games with the Buffalo Sabres last season, posting a 10-16-3 record along with a 3.55 goals-against average and a .891 save-percentage.
The 6-foot-3, 197-pound goaltender was originally drafted by the Pittsburgh Penguins (No. 125 overall) in the 2006 NHL Draft.
Across eight NHL seasons, including stints with the New York Rangers, Arizona Coyotes, Boston Bruins, New York Islanders, Calgary Flames and Buffalo, Johnson has accumulated a 78-61-15 record, a 2.65 goals-against average and a .910 save-percentage.
Internationally, the Saskatoon, Saskatchewan native represented Canada at both the 2010 and 2017 World Championships, earning a silver medal in 2017.