You could make Mango Chutney ( ingredients: diced unripe mangoes,garlic,ginger,cloves, red chilli powder, salt, sugar, raisins). It stores for more than a year at room temperature. If interested in details please PM.
Another option you can make a hot Mango Pickle . In this case I recomend you buy a ready made mix you can buy at Indian stores and follow the instructions on the packet.