I recently created software for a cryptocurrency coin (2ACoin). This allowed users to send each other crypto currency via discord. The program used BlockChain API And Discord API. When the user first joined for the first time they need to register their wallet using the program and then their username and wallet address will be saved in a database. If someone was to send that user coins it would pull the wallet address from the database send the coins and then subtract the coins from the senders wallet.