func (c *Client) AddChild(key string, value string, ttl uint64) (*Response, error) {
	raw, err := c.post(key, value, ttl)
	if err != nil {
		return nil, err
	}
	return raw.Unmarshal()
}
Add a new file with a random etcd-generated key under the given path.
package etcd
func (c *Client) AddChildDir(key string, ttl uint64) (*Response, error) {
	raw, err := c.post(key, "", ttl)
	if err != nil {
		return nil, err
	}
	return raw.Unmarshal()
}