clientv3/compare.go
func (cmp Cmp) WithRange(end string) Cmp {
	cmp.RangeEnd = []byte(end)
	return cmp
}
func (cmp Cmp) WithRange(end string) Cmp {
	cmp.RangeEnd = []byte(end)
	return cmp
}
// WithRange sets the comparison to scan the range [key, end).