func Fib() func() time.Duration {
	a, b := 0, 1
	return func() time.Duration {
		a, b = b, a+b
		return time.Duration(a*10) * time.Millisecond
	}
}
func Fib() func() time.Duration {
	a, b := 0, 1
	return func() time.Duration {
		a, b = b, a+b
		return time.Duration(a*10) * time.Millisecond
	}
}
func Fib ( ) func ( ) time . Duration { a , b := 0 , 1 return func ( ) time . Duration { a , b = b , a + b return time . Duration ( a * 10 ) * time . Millisecond } }
// successive Fibonacci numbers.
successive Fibonacci numbers .