Deep (recursively) merge maps in elixir

deepmerge.ex

defmodule DeepMerge do
  defp _merge(key, v1, v2) when is_map(v1) do    
    Map.merge(v1, v2, &_merge/3)    
  end

  defp _merge(key, v1, v2), do: v2

  def merge(map1, map2) when is_map(map1) and is_map(map2) do
    Map.merge map1, map2, &_merge/3
  end    
end

# example

map1 = %{"top" => %{"name" => "jim"}}
map2 = %{"top" => %{"age" => 22}}

%{"top" => %{"name" => "jim", "age" => 22}} = DeepMerge.merge(map1, map2)