asdf plugin-add io https://github.com/mracos/asdf-io.git
Check asdf readme for instructions on how to install & manage versions of Io.
By default it does not build with the eerie package manager because of different compilation process for versions before (2019.05.22-alpha).
By default it does not build with the addons either, but you can pass a
WITH_IO_ADDONS env var to the install command, e.g.
WITH_IO_ADDONS=true asdf install io $VERSION
2019.05.22-alpha) the addons are now eerie packages, so the flag above will not work
please see IoLanguage/io#400 for more information
Keeping in mind that you'll need the following packages if building with the addons