res.download function is not working in express.js

I want to download a file in node.js using express.js framework according to the get request url.

I didn't get an error in this code, but the file is not downloaded, it shows
success message.

Kindly look at following code, can anyone solve this issue?

var express=require("express");
var bodyparser=require("body-parser");
var app=express();
var path=require("path");
app.get("/download/:folder/:file(*)",function(req,res)
{

var folder=req.params.folder;
var filename=req.params.file;
var downloadlocation=path.join(__dirname,folder,filename);
console.log(downloadlocation);
res.download(downloadlocation,function(err,success)
{
if(err)
{
console.log("download failed try again");
}
else {
console.log("download successfully");
}
});

});

app.listen(8086,function()
{
console.log("server is listening on port 8086");
});

res.download(downloadlocation, filename, function(err,success)

res.download(path [, filename] [, options] [, fn])

filename

downloadlocation=path.join(__dirname,folder,filename)

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