server_groups.go
func (c *Client) AddServersToServerGroup(identifier string, serverIds []string) (*ServerGroup, error) {
	group := new(ServerGroup)
	opts := new(serverGroupMemberOptions)
	for _, id := range serverIds {
		opts.Servers = append(opts.Servers, serverGroupMember{Server: id})
	}
	_, err := c.MakeApiRequest("POST", "/1.0/server_groups/"+identifier+"/add_servers", opts, &group)
	if err != nil {
		return nil, err
	}
	return group, nil
}
func (c *Client) AddServersToServerGroup(identifier string, serverIds []string) (*ServerGroup, error) {
	group := new(ServerGroup)
	opts := new(serverGroupMemberOptions)
	for _, id := range serverIds {
		opts.Servers = append(opts.Servers, serverGroupMember{Server: id})
	}
	_, err := c.MakeApiRequest("POST", "/1.0/server_groups/"+identifier+"/add_servers", opts, &group)
	if err != nil {
		return nil, err
	}
	return group, nil
}
// AddServersToServerGroup adds servers to an existing server group.
//
// The identifier parameter specifies the destination group.
//
// The serverIds paramater specifies the identifiers of the servers you want to add.