If you’re installing Antergos in UEFI mode in Virtualbox, things won’t go so smoothly because you’ll need to setup the EFI boot. You’ll get a message like this:
After that it’ll go into the UEFI Interactive Shell. There, you’ll have to edit the startup.nsh script to add the efi file.
Type FS0: and press enter to open the filesystem
Type edit startup.nsh and press enter to open the editor
Type \EFI\antergos_grub\grubx64.efi and press CTRL + Q to quit, but it asks you to save the file. Do that and press enter again and CTRL + Q again to exit for real.
Type reset and press enter to restart the virtual machine and it should boot your Antergos Linux OS properly.