Discord giveaway bot sample using discord.js

index.js

// Create discord application (bot) : https://discord.com/developers/applications
// discord.js guide : https://discordjs.guide/

const Discord = require('discord.js');
const client = new Discord.Client();

const organizerId = `<enter organizer discord's id here>`;
const botToken = `<enter bot token here>`;

var participants = [];

client.once('ready', () => {
	console.log('Ready!');
});

client.on('message', message => {
	if (message.content === '!giveaway') {
		const participant = message.author.id;
		participants.push(participant);
		message.channel.send(`<@${participant}> registered to the giveaway`);
	} else if (message.content === `!go` && message.author.id === organizerId) {
		const winner = participants[Math.floor(Math.random() * participants.length)];
		message.channel.send(`Congratulations <@${winner}>!`);
    }
});

client.login(botToken);