How to play random sound

I'm making a discord bot, and I want it to play a random mp3 file when it joins channel.

case"join":
            message.delete( {timeout: 5000})
            const voiceChannel = message.member.voice.channel
            if(voiceChannel) {
                const connection = await voiceChannel.join()
                const files = fs.readdirSync("./sounds/")
                const randFile = files[Math.floor(Math.random() * files.length)]
                const dispatcher = connection.play(randFile)
            } else {
                message.reply("you need to be in a voice channel!").then(message => message.delete( {timeout: 5000}))
            }
            break;

When I type $join in chat, it joins voice channel that I'm in but doesn't play anything.