LogMessages.go

package main

import (
    "flag"
    "github.com/bwmarrin/discordgo"
    "fmt"
    "log"
    "os"
    "os/signal"
    "syscall"
)

var (
    Token string
)

func init() {
    flag.StringVar(&Token, "token", "", "Token to listen to. (Prefix \"Bot \" if its a bot account)")
    flag.Parse()
}

func main() {
    bot, err := discordgo.New(Token)
    if err != nil {
        fmt.Println("Couldn't create discordgo instance.")
        log.Fatalln(err)
        return
    }

    bot.AddHandler(onMessageReceived)

    err = bot.Open()
    if err != nil {
        fmt.Println("Couldn't connect to Discord.")
        log.Fatalln(err)
        return
    }

    channel := make(chan os.Signal, 1)
    signal.Notify(channel, syscall.SIGINT, syscall.SIGTERM, os.Interrupt, os.Kill)
    <- channel

    bot.Close()
}

func onMessageReceived(session *discordgo.Session, event *discordgo.MessageCreate) {
    if event.Mentions == nil || len(event.Mentions) == 0 || !contains(event.Mentions, session.State.User) {
        return
    }
    channel, _ := session.Channel(event.ChannelID)
    fmt.Println(channel.GuildID, "-", event.Message.Author.ID, "(" + event.Message.Author.Username + "#" + event.Message.Author.Discriminator + ")::", event.Message.Content)
}

func contains(s []*discordgo.User, e *discordgo.User) bool {
    for _, a := range s {
        if a.ID == e.ID {
            return true
        }
    }
    return false
}