Three days before Cboe Global Markets Inc., one of the world’s biggest regulated exchanges, debuts futures on the cryptocurrency, it had one of its wildest sessions ever. On Coinbase Inc.’s GDAX exchange, prices zoomed up to almost $20,000 from $16,000 in only about 90 minutes — then crashed back down. The largest digital currency is still up more than 16-fold this year.Three days before Cboe Global Markets Inc., one of the world’s biggest regulated exchanges, debuts futures on the cryptocurrency, it had one of its wildest sessions ever. On Coinbase Inc.’s GDAX exchange, prices zoomed up to almost $20,000 from $16,000 in only about 90 minutes — then crashed back down. The largest digital currency is still up more than 16-fold this year.Three days before Cboe Global Markets Inc., one of the world’s biggest regulated exchanges, debuts futures on the cryptocurrency, it had one of its wildest sessions ever. On Coinbase Inc.’s GDAX exchange, prices zoomed up to almost $20,000 from $16,000 in only about 90 minutes — then crashed back down. The largest digital currency is still up more than 16-fold this year.