How to run ecto.create for an Elixir app?

non-existing domain - :nxdomain usually means that IPv6 needs to be enabled.
In order to enable that you will need to make your repo config something like this

config :app, App.Repo,
    ssl: false,
    socket_options: [:inet6],
    url: database_url,
    pool_size: String.to_integer(System.get_env("POOL_SIZE") || "10")