const mysql = require('mysql2');

    let pool  = mysql.createPool({
      connectionLimit : 10,
      host            : 'localhost',
      user            : 'user',
      password        : 'passwd',
      database        : 'database',
      waitForConnections: true,
      queueLimit: 0
    });

    client.mysqllocal = async function localmysql(mySQL_db, mySQL_query){
      let rows;
         pool.getConnection(async function(err, conn) {

          if (err){
            console.log(err);
          }

        conn.changeUser({database : mySQL_db}, function(err) {
          if (err){
            console.log(err);
          }
        });

          conn.query(mySQL_query), function (error, results, fields) {
            rows = results
          }
        conn.release()
      })
      return rows;
    }

    let func = client.mysqllocal('database','SELECT * FROM `guild_config` WHERE `guild_id` = "guildid"');
    console.log(func);