https www to non www (NGINX) - node.js

Question

Im new to all this, but how do i redirect my from www to a non-www. I have tried multiple ways to fix it in NGINX but no mater how i change it, there is still a www and an non-www site. The payment gateway is redirected to a non-www website after a transaction.
server {
server_name example.com www.example.com;
location / {
proxy_pass http://123.0.0.1:5000;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
proxy_redirect off;
}
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/dineshudayan.tech/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/dineshudayan.tech/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server {
if ($host = example.com) {
return 301 https://$host$request_uri;
} # managed by Certbot
if ($host = www.example.com) {
return 301 https://$host$request_uri;
} # managed by Certbot
listen 80;
server_name www.example.com;
return 404; # managed by Certbot
}
server {
listen 80;
server_name admin.example.com www.admin.example.com;
location / {
proxy_pass http://123.0.0.1:8000;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
proxy_redirect off;
}
}

Answer 1

#richard-smith is right; here's a fully worked example with some comments:
# Your default server - assuming DNS is set up correctly
# will serve http & https requests for any *.example.com
# hosts and redirect to them to https://example.com
server {
listen 80 default_server;
listen 443 ssl default_server;
server_name www.example.com;
ssl_certificate /etc/letsencrypt/live/dineshudayan.tech/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/dineshudayan.tech/privkey.pem;
include /etc/letsencrypt/options-ssl-nginx.conf;
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;
# redirect all requests to https://example.com
return 301 https://example.com$request_uri;
}
# http server for example.com
# - will redirect requests to https://example.com
server {
listen 80;
server_name example.com;
# redirect all requests to https://example.com
return 301 https://example.com$request_uri;
}
# Your example.com https server
server {
listen 443 ssl;
server_name example.com;
ssl_certificate /etc/letsencrypt/live/dineshudayan.tech/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/dineshudayan.tech/privkey.pem;
include /etc/letsencrypt/options-ssl-nginx.conf;
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem;
}