Add use Spooks.Workflow to your workflow module to enable the @step attribute.

Example

defmodule MyWorkflow do
  use Spooks.Workflow

  @step %Step{in: StartEvent, out: StepOneEvent}
  def start_step(%StartEvent{} = start_event, %SpooksContext{} = ctx) do
    {:ok, ctx, %StepOneEvent{}}
  end
end