function onMessage(event) {

  // Handles regular onMessage logic.
  // Evaluates if and handles for all slash commands.
  if (event.message.slashCommand) {
    switch (event.message.slashCommand.commandId) {

      case SLASHCOMMAND.DIALOG: // Displays meeting dialog for /schedule_Meeting.

        // TODO update this with your own logic to set meeting recipients, subjects, etc (e.g. a group email).
        return getInputFormAsDialog_({
          invitee: '',
          startTime: getTopOfHourDateString_(),
          duration: 30,
          subject: 'Status Stand-up',
          body: 'Scheduling a quick status stand-up meeting.'
        });

      case SLASHCOMMAND.HELP: // Responds with help text for /help.
        return getHelpTextResponse_();

      /* TODO Add other use cases here. E.g:
      case SLASHCOMMAND.NEW_FEATURE:  // Your Feature Here
        getDialogForAddContact(message);
      */

    }
  }
  else {
    // Returns text if users didn't invoke a slash command.
    return { text: 'No action taken - use Slash Commands.' }
  }
}
Responds to a MESSAGE event triggered in Chat.
Called when the Chat app is already in the space and the user invokes it via @mention or / command.
Returns a message object containing the Chat app's response. For this Chat app, the response is either the
help text or the dialog to schedule a meeting.

@param {object} event The event object from Google Chat
@return {object} JSON-formatted response as text or Card message