Added state interface for customizing

bot.go

@@ -15,7 +15,7 @@ type bot struct {
 	echo.API
 	data  StateData
 	lock  sync.Mutex
-	state *State
+	state Runnable
 }
 
 func (b *bot) Update(u *echo.Update) {

state.go

@@ -9,18 +9,18 @@ import (
 type StateData map[string]interface{}
 
 type Runnable interface {
-	Call(*Update) (*State, error)
+	Call(*Update) (Runnable, error)
 }
 
 type State struct {
 	fn stateFn
 }
 
-func (s *State) Call(u *Update) (*State, error) {
+func (s *State) Call(u *Update) (Runnable, error) {
 	return s.fn(u)
 }
 
-type stateFn func(*Update) (*State, error)
+type stateFn func(*Update) (Runnable, error)
 
 func (d StateData) Set(name string, data interface{}) {
 	d[name] = data
@@ -49,7 +49,7 @@ var EchoState = State{
 	fn: EchoFunc,
 }
 
-func EchoFunc(u *Update) (*State, error) {
+func EchoFunc(u *Update) (Runnable, error) {
 	u.AnswerText(u.Text(), &echotron.MessageOptions{})
 	return nil, nil
 }