code: func (api *Client) GetChannelsContext(ctx context.Context, excludeArchived bool, options ...GetChannelsOption) ([]Channel, error) {
  	config := channelsConfig{
  		values: url.Values{
  			"token": {api.token},
  		},
  	}
  	if excludeArchived {
  		options = append(options, GetChannelsOptionExcludeArchived())
  	}
  
  	for _, opt := range options {
  		if err := opt(&config); err != nil {
  			return nil, err
  		}
  	}
  
  	response, err := api.channelRequest(ctx, "channels.list", config.values)
  	if err != nil {
  		return nil, err
  	}
  	return response.Channels, nil
  }
docs: // GetChannelsContext retrieves all the channels with a custom context
  // see https://api.slack.com/methods/channels.list