A naive circular buffer ...

queue.go

// A naive circular buffer ...
type CircularBuffer struct {
	buf        []int
	cap, head, tail int
}

func (q *CircularBuffer) add(d int) error { 
	if q.tail-q.head > q.cap {
		return errors.New("buffer full")
	}
	q.buf[q.tail%q.cap] = d
	q.tail += 1
	return nil
}

func (q CircularBuffer) remove() (int, error) {
	if q.tail == q.head {
		return -1, errors.New("buffer empty")
	}
	x := q.buf[q.head%q.cap]
	q.head += 1
	return x, nil
}