What you see: Clear sticky stuff around the stem of your mango
What it is: Sap!
Eat or toss: The mango is fine to eat. Clear sap near the stem doesn’t indicate anything problematic about the interior of the fruit. 

The story:
Mangos pack a lot of liquid, so much so that when they’re first harvested, they’re known to squirt streams of milky sap. University of Florida professor Jeffrey Brecht tells me they can squirt as high as a foot in the air!

That initial burst is acidic, and without proper handling can burn skin—both on mangos and on people. Eventually, however, the milky sap switches over to something more innocuous and clear. You tend to see that transparent, sticky liquid accumulate around the stem because that’s where it’s escaping from.

The amount of sap is determined by how water-saturated the mango tree was when the fruit was picked. If, say, it rained shortly before harvest, there would be more pressure and a higher volume of liquid ready to spray and leak. 

SOURCES:
Jeffrey Brecht. Post-harvest plant physiologist. Professor of horticultural science. University of Florida. Mango: PostHarvest Best Management Practices Manual. Edited by Jeffrey Brecht. University of Florida Extension. Mango Board. 

“If you wait for the mango fruits to fall, you'd be wasting your time while others are learning how to climb the tree.”
― Michael Bassey Johnson, Master of Maxims