If you see
Copysignature from "Antergos Build Server (Automated Package Build System) <admin@antergos.org>" is unknown trust
signature from "Antergos Build Server (Automated Package Build System) <admin@antergos.org>" is unknown trust
execute:
Copysudo pacman-key --refresh-keys sudo pacman -Sy antergos-keyring
sudo pacman-key --refresh-keys sudo pacman -Sy antergos-keyring