$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt install python-certbot-nginx

ubuntu@ip-172-31-5-89:/srv/Neo-News/.config/nginx$ sudo certbot --nginx -d neonews.site # 해당 dns에 대한 개인키, 공개키 생성해준다
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator nginx, Installer nginx
Cert not yet due for renewal
You have an existing certificate that has exactly the same domains or certificate name you requested and isn't close to expiry.
(ref: /etc/letsencrypt/renewal/neonews.site.conf)
What would you like to do?
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1: Attempt to reinstall this existing certificate
2: Renew & replace the cert (limit ~5 per 7 days)
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Select the appropriate number [1-2] then [enter] (press 'c' to cancel): 1 # 번호 선택해야 한다
Keeping the existing certificate
Deploying Certificate to VirtualHost /etc/nginx/sites-enabled/mysite.conf
Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.
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1: No redirect - Make no further changes to the webserver configuration.
2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for
new sites, or if you're confident your site works on HTTPS. You can undo this
change by editing your web server's configuration.
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Select the appropriate number [1-2] then [enter] (press 'c' to cancel): 2 # 번호 선택해야 한다
No matching insecure server blocks listening on port 80 found.
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Congratulations! You have successfully enabled https://neonews.site
You should test your configuration at:
https://www.ssllabs.com/ssltest/analyze.html?d=neonews.site
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IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/neonews.site/fullchain.pem # 생성된 공개키 path
   Your key file has been saved at:
   /etc/letsencrypt/live/neonews.site/privkey.pem # 생성된 개인키 path
   Your cert will expire on 2021-11-14. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot again
   with the "certonly" option. To non-interactively renew *all* of
   your certificates, run "certbot renew"
 - If you like Certbot, please consider supporting our work by:
   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

/etc/letsencrypt/live/neonews.site/fullchain.pem # 생성된 공개키 path
/etc/letsencrypt/live/neonews.site/privkey.pem # 생성된 개인키 path

$ sudo certbot renew --dry-run

server {
    listen 80;
    server_name neonews.site;
    charset utf-8;
    return 301 https://$host$request_uri;
    }
server {
    listen 443 ssl;
    server_name neonews.site;
    ssl_certificate /etc/letsencrypt/live/neonews.site/fullchain.pem; # 공개키
    ssl_certificate_key /etc/letsencrypt/live/neonews.site/privkey.pem; # 개인키
    charset utf-8;
    client_max_body_size 128M;
    location / {
        uwsgi_pass  unix:///tmp/mysite.sock;
        include     uwsgi_params;
    }
    location /static/  {
        alias /srv/Neo-News/static/;
    }
}

ubuntu@ip-172-31-5-89:/srv/Neo-News$ sudo cp -f /srv/Neo-News/.config/nginx/mysite.conf /etc/nginx/sites-available/mysite.conf # 프로젝트에 있는 nginx 내용 available에 복사
ubuntu@ip-172-31-5-89:/srv/Neo-News$ sudo ln -sf /etc/nginx/sites-available/mysite.conf /etc/nginx/sites-enabled/mysite.conf # 서버에 존재하는 sites-enabled에도 똑같이 적용
ubuntu@ip-172-31-5-89:/srv/Neo-News$ sudo systemctl daemon-reload && sudo systemctl # 변경후 reload를 잊지말자