Apart from all these changes mentioned in doc: https://pub.dev/packages/just_audio_background

I needed MainActivity to extend AudioServiceActivity and also neede MediaTag() to those audios that need to be played in background

await _audioPlayer.setAudioSource(
  AudioSource.asset(
    "assets/audio/db12/$currentKey.wav",
    tag: MediaItem(
      id: currentKey,
      album: "album",
      title: "title",
      artist: "flutter jackson",
    ),
  ),
);