Peel corn and place in boiling water to cook for a couple of minutes. Remove from heat, drain, let cool, and then cut niblets off the cobs.
Optional (but delicious) quick fry the niblets in a hot dry cast iron skillet if oil free (or add 1 tsp of oil) with coarse black pepper, a sprinkle of sea salt, and red pepper flakes just until slightly charred (about 2-3 minutes).
If you are using frozen corn, let it thaw, and then use the quick fry method above. Set aside to cool. Cut mango into bite-size cubes (if you've never done this before, here's a helpful video) and place them in a medium-sized bowl. *Leave the mango pieces a bit bigger if you like a chunky salsa or cut into smaller pieces for a finer salsa. To the mango and corn, add the chopped red onion, minced jalapeño peppers, lime juice, and apple cider vinegar.
Top with chopped fresh cilantro, a pinch of cayenne pepper, S&P, and hot pepper flakes. Toss to incorporate.
Taste and adjust flavours as necessary. If the salsa tastes bland, add more salt. Not tangy enough, add lime or apple cider vinegar. Add more jalapeño or cayenne to bump up the spice level.