iterator.go
func (it *Iterator) Seek(key []byte) (found bool) {
	var next *node
	_, next, found = it.seekForBaseSplice(key)
	present := it.setNode(next, false)
	return found && present
}
func (it *Iterator) Seek(key []byte) (found bool) {
	var next *node
	_, next, found = it.seekForBaseSplice(key)
	present := it.setNode(next, false)
	return found && present
}
// Seek searches for the record with the given key. If it is present in the
// skiplist, then Seek positions the iterator on that record and returns true.
// If the record is not present, then Seek positions the iterator on the
// following node (if it exists) and returns false.