/*
* ERROR
*/

const err = new MongooseError('Query was already executed: ' + str);

CODE:

client.on('messageCreate', async (message) => {
    if(message.author.bot) return
    let messageUser = await messages.findOne({
    memberID: message.author.id,
    guildID: message.guild.id,
  });

  if(!messageUser) {
    messageUser = new messages({
        memberID: message.author.id,
        guildID: message.guild.id,
        messageCount: 0
    });

    await messageUser.save().catch(e => console.log(e));
    return messageUser;
  };

    await messages.findOne({
        memberID: message.author.id,
        guildID: message.guild.id
    }, async (err, data) => {
        data.messageCount += 1;
      await data.save().catch(e => console.log(e));
    })
})