Need 1 nginx vhost redirecting non-www to www and http to https

Hi there,

I've struggled with this for hours now and no matter what i tried its not 100% working. I got a free security certificate from letsencrypt for www.knightsenglish.com but it is only valid for www.knightsenglish.com so if you browse there without www its invalid.

This all should work like this:
browsing to http://knightsenglish.com or http://www.knightsenglish.com or https://knightsenglish.com
should all redirect you to https://www.knightsenglish.com

Here is what I got so far: /etc/nginx/sites-enabled/knightsenglish.com.conf

Code:

server {
        # redirecting http port 80 to https port 443 and adding www
        listen 80;
        server_name www.knightsenglish.com knightsenglish.com;
        return 301 https://www.knightsenglish.com$request_uri;
}
server
{
        listen 443 ssl;
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_certificate /etc/ssl/private/www.knightsenglish.com.crt;
        ssl_certificate_key /etc/ssl/private/www.knightsenglish.com.key;
        server_name www.knightsenglish.com;

and this is not working: https://knightsenglish.com its not adding WWW.

I could easily get a certificate for the non-www version, would that be easier? I'm looking for an elegant solution here.
Do I possibly need 4 server declarations? 2 for each www and non-www (http+https)?