stun gun vs melee

how does a person counter this shit. every time i play heavy melee all lights switch to stun gun and i can't do anything it, i'd be fine if they do it when i'm actively chasing them but most of the time they go out of their ways to get a free kill on me. I just want to know way to counter.

EDIT : for the record I'm aware that stun gun is a counter for melee. I'd like to keep playing melee and not switch off of it. All I want is ways to make it where i'm not an easy free kill