Nginx – node.js https/www redirect to https non-www on nginx

I'm using nginx for my node.js app.
I've used the Digitalocean tutorial to config the nginx and https use.
Right now, the following works:

http:// example.com -> https:// example.com
example.com –> https:// example.com
www.example.com –> https:// example.com
http:// www.example.com –> https:// example.com

but when i enter https:// www.example.com, it does not redirect to https:// example.com

here is my nginx congif on sites-available/default

# HTTP - redirect all requests to HTTPS:
server {
        listen 80;
        listen [::]:80 default_server ipv6only=on;
        return 301 https://$host$request_uri;
}

# HTTPS - proxy requests on to local Node.js app:
server {
        listen 443;
        server_name ezplan.ir;

        ssl on;
        # Use certificate and key provided by Let's Encrypt:
        ssl_certificate /path/to.crt;
        ssl_certificate_key /path/to.key;
        ssl_session_timeout 5m;
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_prefer_server_ciphers on;
        ssl_ciphers 'SSL STUFF';

        # Pass requests for / to localhost:8080:
        location / {
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header X-NginX-Proxy true;
                proxy_pass http://localhost:8080/;
                proxy_ssl_session_reuse off;
                proxy_set_header Host $http_host;
                proxy_cache_bypass $http_upgrade;
                proxy_redirect off;
        }
}

can anyone help me do this redirection as well?