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

client.login("token").then(() => {
    console.log("Ready message");
    var guild = client.guilds.get('Guild ID goes here');
    if(guild && guild.channels.get('Channel ID goes here')){
        guild.channels.get('Server ID goes here').send("Message goes here").then(() => client.destroy());
    } else {
        console.log("Didn't work");
    }
    client.destroy();
});