func (n *node) next() *node {
	if len(n.forward) == 0 {
		return nil
	}
	return n.forward[0]
}
next returns the next node in the skip list containing n.
package skiplist
import (
	"math/rand"
)
const p = 0.25
const DefaultMaxLevel = 32
type node struct {
	forward    []*node
	backward   *node
	key, value interface{}
}