You can use .setProxy() method of session object. You're able to specify proxy directly like in example below:

// in main.js

var electron      = require('electron');

var BrowserWindow = electron.BrowserWindow;

mainWindow = new BrowserWindow({

    width: 970,

    height: 500,

    center: true,

    'title': 'Main window',

});

mainWindow.webContents.session.setProxy({proxyRules:socks5://114.215.193.156:1080}, function () {

    mainWindow.loadURL('https://whatismyipaddress.com/');

});

Or you can use PACscript:

// in main.js

mainWindow.webContents.session.setProxy({pacScript:file://+root+/js/pacfile.js}, function () {

    mainWindow.loadURL('https://whatismyipaddress.com/');

});





// pacfile.js example

var blocked      = [site1.com, site2.com, site3.com];

var proxyServer  = SOCKS5 114.215.193.156:1080;

function FindProxyForURL(url, host) {

    var shost = host.split(.).reverse();

    shost = shost[1] + . + shost[0];

    for(var i = 0; i < blocked.length; i++) {

        if( shost == blocked[i] ) return proxyServer;

    }

    return DIRECT;

}