code: func (api *Client) PostEphemeral(channelID, userID string, options ...MsgOption) (string, error) {
  	return api.PostEphemeralContext(
  		context.Background(),
  		channelID,
  		userID,
  		options...,
  	)
  }
docs: // PostEphemeral sends an ephemeral message to a user in a channel.
  // Message is escaped by default according to https://api.slack.com/docs/formatting
  // Use http://davestevens.github.io/slack-message-builder/ to help crafting your message.