plaintextGolang

    data, err := os.ReadFile("yourfile.bin")
    if err != nil {
        return nil, err
    }

    reader := bytes.NewReader(data)
    var length uint32
    if err := binary.Read(reader, binary.BigEndian, &length); err != nil {  // read the length of the first message (plaintext)
        return nil, err
    }

    packet := make([]byte, length-4) // [-4](length as u32)
    if err := binary.Read(reader, binary.BigEndian, packet); err != nil {   //  read the first message
        return nil, err
    }

    plaintextMgs := new(spotify.ClientResponsePlaintext)
    if err := proto.Unmarshal(packet, plaintextMsg); err != nil {   //  unmarshal and do whatever you want with plaintext message
        return nil, err
    }