This can easily be done from your dns configuration with cname. Or you can use nginx to redirect www to the naked one. Either way is ok. 

CNAME is used for resolving domain to other another domain - as an alias. CNAME records are often used to point to a host or to point the "www" version of the domain to the naked domain. This record is fairly popular for web development platforms like Wix and Squarespace. Since CNAME is an alias record, it can be a bit confusing and also be damaging if not used properly

Nginx config you add this

server {
    server_name  www.domain.com;
    rewrite ^(.*) http://domain.com$1 permanent;
}

I recommend you to use a reverse proxy and to permanently redirect one to the other. This way you can also avoid that your website is indexed twice by the search engines.