If you install Neovim and open up a new nvim session, you might notice that none of your carefully crafted ~/.vimrc configuration is taking effect.
This is because the ~/.vimrc file is not part of Neovim's default runtimepath (see :h runtimepath for details on what is included).
For custom user-land configuration of your Neovim sessions, you should start with an init.vim file. For Mac users, it will likely be placed in ~/.config/nvim/. To be sure where it belongs, you can run :echo stdpath('config').
In that file, you can add any Neovim-specific configuration. You can also take the opportunity to source your ~/.vimrc file so that you get all those configurations. These lines will do the trick.
if filereadable(expand('~/.vimrc'))
source ~/.vimrc
endif
Things tend to be backward compatible, so you aren't likely to run into issues with what's in your ~/.vimrc. At any rate, it is a good starting point for getting back to a familiar configuration.
See :h nvim for more details about how to transition.