make your function async and then await xyz()
var http = require('http');
var foo = async function(req, res){
var a = await xyz('5');
res.end(a);
console.log(a);
}
function xyz(arg){
var aa = 55;
return aa;
}
http.createServer(foo).listen(8000);
console.log('start server');
2
solved NodeJs function wait until callback return value