Generic task

gen_task.ex

defmodule GenTask do
  def async do
    parent = self()

    spawn(fn ->
      receive do
        {:resolve, value} -> send parent, {self(), :result, value}
        {:reject, reason} -> send parent, {self(), :reject, reason}
      end
    end)
  end

  def resolve(pid, value) do
    send pid, {:resolve, value}
  end

  def reject(pid, reason) do
    send pid, {:reject, reason}
  end

  def await(pid) do
    receive do
      {^pid, :result, value} -> {:ok, value}
      {^pid, :reject, reason} -> {:error, reason}
    end
  end
end