get audio length

axios({
          method: "get",
          url: rec_Url,
          responseType: "stream"
        }).then(function (response) {
          response.data.pipe(fs.createWriteStream("./my.mp3"));
        }).then(() => {
          // From a local path...
          mm.parseFile('./my.mp3')
            .then(metadata => {
              console.log(metadata);
            })
          // make sure you set the correct path to your video file
          var proc = ffmpeg('./images/image.png')
            // loop for 5 seconds
            // .loop()
            .input(rec_Url)
            // setup event handlers
            .on('end', function () {
              console.log('file has been converted succesfully');
            })
            .on('error', function (err) {
              console.log('an error happened: ' + err.message);
            })
            // save to file
            .save('./newpost.mp4');
        })