code: func (api *Client) InviteUserToGroupContext(ctx context.Context, group, user string) (*Group, bool, error) {
  	values := url.Values{
  		"token":   {api.token},
  		"channel": {group},
  		"user":    {user},
  	}
  
  	response, err := api.groupRequest(ctx, "groups.invite", values)
  	if err != nil {
  		return nil, false, err
  	}
  	return &response.Group, response.AlreadyInGroup, nil
  }
docs: // InviteUserToGroupContext invites a specific user to a private group with a custom context