serve.1.js

const File      = require('../models/file')
const fs        = require('fs')

exports.getFile = async function (request, response) {
    let file = null 
    try { file = await File.findById(request.params.id) } catch (err) {}

    if (!file) {
        return response.status(404).json({
            "data": {
                "error": "unable to find requested file"
            }
        })
    }

    var stat = fs.statSync(file.location)
    response.writeHead(200, {
        'Content-Type': file.mime,
        'Content-Length': stat.size,
        'Content-Disposition': `attachment;filename=${file.name}`
    })

    let stream = fs.createReadStream(file.location)
    stream.pipe(response)
}