Shell Script To Automate Nginx Blocks - shell

Question

I'm trying to automate nginx setup through the script
Command - SECRET_KEY='xxxx' HTTP='$http_update' AMCU_HOST='$host' AMCU_RURI='$redirect_uri' sh ./script.sh domain.com port username
In the server block file, I want HTTP='$http_update' but it replaces it and just leave blank ''. Same for AMCU_HOST='$host' and AMCU_RURI='$redirect_uri'. Tried without attributes in command but same happens again...leaves '' as script thinks it as $ attr.
script.sh
#!/bin/bash
domain=$1
port=$2
user=$3
block="/etc/nginx/sites-available/$domain"
ssh="/home/$user/.ssh/authorized_keys"
#Create User
echo "▶ Creating User"
sudo useradd $user
#User mkdir
echo "▶ Updating home dir"
sudo mkdir /home/$user
#Create .ssh/authkeys
echo "▶ Updating SSH dir"
cd /home/$user && mkdir .ssh/
#Create the SSH Auth file:
echo "▶ Updating SSH AuthKey"
sudo tee $ssh > /dev/null <<EOF
$SECRET_KEY
EOF
#Create the Nginx server block file:
echo "▶ Updating NGINX Server Block"
sudo tee $block > /dev/null <<EOF
server {
listen 80;
server_name $domain;
return 301 https://$domain$AMCU_RURI;
}
server {
#Secure HTTP (HTTPS)
listen 443 ssl;
server_name $domain;
error_page 500 502 503 504 /500.html;
location /500.html {
root /var/www/html;
internal;
}
ssl_certificate /etc/letsencrypt/live/$domain/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/$domain/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
location / {
proxy_pass http://localhost:$port;
proxy_http_version 1.1;
proxy_set_header Upgrade $HTTP;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $AMCU_HOST;
proxy_cache_bypass $HTTP;
}
}
EOF
#Link to make it available
echo "▶ Linking Server Blocks"
sudo ln -s $block /etc/nginx/sites-enabled/
#Test configuration and reload if successful
echo "▶ Reloading Server"
sudo nginx -t && sudo service nginx reload