package main
import (
    "context"
    "fmt"
    "github.com/looplab/fsm"
)
func main() {
    fsm := fsm.NewFSM(
        "closed",
        fsm.Events{
            {Name: "open", Src: []string{"closed"}, Dst: "open"},
            {Name: "close", Src: []string{"open"}, Dst: "closed"},
        },
        fsm.Callbacks{},
    )
    fmt.Println(fsm.Current())
    err := fsm.Event(context.Background(), "open")
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(fsm.Current())
    err = fsm.Event(context.Background(), "close")
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(fsm.Current())
}

package main
import (
    "context"
    "fmt"
    "github.com/looplab/fsm"
)
type Door struct {
    To  string
    FSM *fsm.FSM
}
func NewDoor(to string) *Door {
    d := &Door{
        To: to,
    }
    d.FSM = fsm.NewFSM(
        "closed",
        fsm.Events{
            {Name: "open", Src: []string{"closed"}, Dst: "open"},
            {Name: "close", Src: []string{"open"}, Dst: "closed"},
        },
        fsm.Callbacks{
            "enter_state": func(_ context.Context, e *fsm.Event) { d.enterState(e) },
        },
    )
    return d
}
func (d *Door) enterState(e *fsm.Event) {
    fmt.Printf("The door to %s is %s\n", d.To, e.Dst)
}
func main() {
    door := NewDoor("heaven")
    err := door.FSM.Event(context.Background(), "open")
    if err != nil {
        fmt.Println(err)
    }
    err = door.FSM.Event(context.Background(), "close")
    if err != nil {
        fmt.Println(err)
    }
}