Простой конечный автомат, похожий на Symfony Workflow.

Пример

 1o := new(ObjectImplementedPlaceer)
 2
 3w := NewWorkflow("Start")
 4w.AddTransition("Start", "A")
 5w.AddTransition("Start", "B")
 6w.AddTransition("A", "C")
 7w.AddTransition("B",  "D")
 8w.AddTransition( "C", "D")
 9w.AddTransition("C", "Finish")
10w.AddTransition("D", "Finish")
11
12w.Can(o, "A") // == nil
13w.Can(o, "C") // == ErrTransitionNotFound
14
15w.GetEnabledTransitions(o) // []Place{"A", "B"}
16w.Apply(o, "A") // o now at "A" place
17w.GetEnabledTransitions(o) // []Place{"C"}
18
19w.DumpToDot() // See above

Дамп в формат dot

digraph {
    Start[color="blue"]
    Start -> A[label="Start → A"];
    Start -> B[label="Start → B"];
    A -> C[label="A → C"];
    B -> D[label="B → D"];
    C -> D[label="C → D"];
    C -> Finish[label="C → Finish"];
    D -> Finish[label="D → Finish"];
}

digraph {
    Start[color="blue"]
    Start -> A[label="Start → A"];
    Start -> B[label="Start → B"];
    A -> C[label="A → C"];
    B -> D[label="B → D"];
    C -> D[label="C → D"];
    C -> Finish[label="C → Finish"];
    D -> Finish[label="D → Finish"];
}