free ssl for server for nodejs app more info https://code.lengstorf.com/deploy-nodejs-ssl-digitalocean https://www.youtube.com/watch?v=kR06NoSzAXY

etc_nginx_sites-enabled_default

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

# HTTPS — proxy all requests to the Node app
server {
    # Enable HTTP/2
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name app.example.com;

    # Use the Let’s Encrypt certificates
    ssl_certificate /etc/letsencrypt/live/app.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/app.example.com/privkey.pem;

    # Include the SSL configuration from cipherli.st
    include snippets/ssl-params.conf;

    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:5000/;
        proxy_ssl_session_reuse off;
        proxy_set_header Host $http_host;
        proxy_cache_bypass $http_upgrade;
        proxy_redirect off;
    }
}

letsencrypt_command.sh

# Install tools that Let’s Encrypt requires
sudo apt-get install bc

# Clone the Let’s Encrypt repository to your server
sudo git clone https://github.com/letsencrypt/letsencrypt /opt/letsencrypt
# Move into the Let’s Encrypt directory
cd /opt/letsencrypt

# Create the SSL certificate
./letsencrypt-auto certonly --standalone

# For auto renew
/opt/letsencrypt/letsencrypt-auto renew

nginx.sh

sudo apt-get install nginx

# line 16 17 26
sudo nano /etc/nginx/sites-enabled/default

# openssl
sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048

sudo nano /etc/nginx/snippets/ssl-params.conf

sudo nginx -t

sudo systemctl start nginx

ssl-params.conf

# See https://cipherli.st/ for details on this configuration
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH";
ssl_ecdh_curve secp384r1; # Requires nginx >= 1.1.0
ssl_session_cache shared:SSL:10m;
ssl_session_tickets off; # Requires nginx >= 1.5.9
ssl_stapling on; # Requires nginx >= 1.3.7
ssl_stapling_verify on; # Requires nginx => 1.3.7
resolver 8.8.8.8 8.8.4.4 valid=300s;
resolver_timeout 5s;
add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload";
add_header X-Frame-Options DENY;
add_header X-Content-Type-Options nosniff;

# Add our strong Diffie-Hellman group
ssl_dhparam /etc/ssl/certs/dhparam.pem;