Reminder: 64-bit Requirement for Mac Apps
Starting January 31, new apps submitted to the Mac App Store must support 64-bit, and Mac app updates and existing apps must support 64-bit starting June 2018. If you distribute your apps outside the Mac App Store, we highly recommend distributing 64-bit binaries to make sure your users can continue to run your apps on future versions of macOS. Build and submit your apps using Xcode 9.2.
Learn more about distributing Mac apps