async_query.ex

def async_query(pid, statement, params) do
  message = {:query, statement, params}
  process = GenServer.whereis(pid)
  monitor = Process.monitor(process)
  from = {self(), monitor}

  :ok = Connection.cast(pid, {message, from})
  %Task{ref: monitor}
end

def handle_cast({{:query, _, _} = command, {_, monitor} = from}, s) do
  handle_call(command, from, s)
end