The promising teenage goalkeeper has been training alongside first team stoppers Ofir Marciano, Matt Macey and Kevin Dabrowski and has also featured in matchday warm-ups for Jack Ross' side.
He signed a new deal at Easter Road in January but recently spent time on trial with Manchester City amid interest from a number of English Premier League clubs.
However, according to reports, Wolves are set to win the race for Johnson with a £250,000 deal that would also net Hibs further incentives and add-ons.
The academy graduate was called up by Scotland Under-17s last year having been capped three times at Under-16 level.
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It has also been reported that Hibs striker Ethan Laidlaw, a former Easter Road ball boy who recently signed his first professional contract, spent last week on trial at Leeds United.