macOS Catalina does not support running 32-bit apps.

Time to remove darwin/386 support soon? (@rsc always liked keeping it around as an easy way to hack on the 386 port on his laptop, but sounds like that reason is going away. We might even be able to remove it earlier, once Russ upgrades his laptop.)

Might be worth noting that it's going away soon in the Go 1.14 release notes.