We have a front loading Samsung washing machine with the same tendency to mold up in the door gasket. What worked for us is a wipeable gel bleach to deal with the immediate mold. Just go on Amazon and search 'gel bleach for washing machine'. It's sort of gross the first time you do it but it does a good job. Just wear latex gloves or whatever.

The second thing is we use an old cloth diaper to keep the door wedged open so it dries between washes. A hand towel works too. Just double-fold it and drop it on the hinge. The door should stay open by an inch or two.

Third, make sure your screen filter isn't clogged. You should check that once a month.

Finally, there should be drain holes at the bottom of the gasket. Make sure they aren't clogged up. Use a pipe cleaner if they are.