I want to get returned value in other file

index.js

var radium = require("include.js");
console.log(radium.GetUsername()); //undefined

include.js

function GetUsername() {
    db.get("SELECT * FROM users WHERE id = 1",[],function(err,user) {
        console.log(user['username']); //works
        return user['username'];
    });
}
module.exports.GetUsername = GetUsername;