Before this change, Android and iOS were special for two reasons:
app.Main would return immediately, and the program main was invoked from
a goroutine. We can reduce that to one special case by either
- run the program main from the main thread,
- or make app.Main block.
Choose to run main on the main thread.
Signed-off-by: Elias Naur <mail@eliasnaur.com>