Boro winger on the verge of joining CSKA Sofia
According to reports, the 29-year-old has been linked with a move to CSKA Sofia in the summer transfer window.
According to 24chasa, an "informed source" has claimed that CSKA Sofia are "on the verge of signing" the 29-year-old winger.
Johnson joined Boro in August 2017, on a three-year deal from Oxford United, for a fee around £2.7 million.
The Birmingham born winger made his debut for Boro in a 3-0 win away to Bolton, however, spent the 2018/2019 season on loan with Sheffield United.
Johnson has made 32 appearances for Boro this season, scoring one goal.