Why set log.transports.file.file doesn't work?

Hello.

In my project(use electron & vue), I configure the transport formats in main.js like this.

```
const logFormat = '{h}:{i}:{s}:{ms} {text}'
log.transports.console.format = logFormat
log.transports.console.format = (msg) => util.format.apply(util, msg.data);

const appDataDir = path.join(app.getPath('appData'), 'my-project')
log.transports.file.level = 'info'
log.transports.file.format = logFormat
log.transports.file.maxSize = 5 * 1024 * 1024
log.transports.file.file = path.join(appDataDir, 'log.log')
log.transports.file.streamConfig = { flags: 'w' }
log.transports.file.stream = fs.createWriteStream('log.log')

1. This works in dev mode, except the log file does not in the path of configuration(appDataDir/log.log), but the project folder in my desktop.

2.When I build my app with electron builder and run, it shows me an error of 
"**Uncaught Exception:
Error: EACCES: permission denied, open 'log.log**'"

Am I wrong with something? How can this be fixed please.

[megahertz]

In most cases, the application directory is not writable after installation. That’s why default log path is inside appData directory. I think it’s not very easy to make it writable on windows, and it’s impossible on linux and mac.

[megahertz]

no problem)