I would think the shark would likely try and suck the slime off the gourami, leaving it open to disease. Also sharks can be quite active at times and gourami may be stressed with the constant movement.
From my experience with the similar red-tailed shark, it depends on tank size and fish size. You will obviously be better off with a larger tank. If the gourami is the same size or larger as the shark, again from my experience it will USUALLY(of course, there can be exceptions) defend itself with minimal harm done to any fish.
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