redirect non-www to www with or without ssl in ngnix

ngnix.conf

# http://domain.com     -> https://www.domain.com
# http://www.domain.com -> https://www.domain.com
server {
  listen 80;
  server_name domain.com www.domain.com;
  return 301 https://www.domain.com$request_uri;
}

# https://domain.com    -> https://www.domain.com
server {
  listen 443 ssl;
  server_name domain.com;

  ssl_certificate /data/unified.crt;
  ssl_certificate_key /data/my-private-decrypted.key;

  return 301 https://www.domain.com$request_uri;
}

server {
  listen 443 ssl;
  server_name www.domain.com;

  ssl_certificate /data/unified.crt;
  ssl_certificate_key /data/my-private-decrypted.key;

  location / {
    proxy_pass http://domain.com:3000;
    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;
  }
}