Possible things that might help:
Water it less.
Keep the surface drier by "top-dressing" with something very coarse like small gravel or bark chunks. The surface should not be decomposable (not be rapidly edible by fungi).
If you have a draftier spot with good light, try that or a small fan aimed at the soil surface.
Use a potting mix with less or no decomposable organic matter. Compost is helpful in in-ground-soil, but risky in containers.
Use a potting mix that drains faster and holds less water.
Move it to a much smaller pot for the first several years.
Pick out or scrape off the fungi as you see them. (This is practical because the fungi are probably not harmful.
You could also ignore the fungus. No fungus gnats yet, right?