Get acme.sh

curl https://get.acme.sh | sh

Then you can find ~/.acme.sh/acme.h

If you can't access raw.githubusercontent.com: curl: (7) Failed connect to raw.githubusercontent.com:443; Connection

You need figure out the ip address your self by:

The Best IP Address, Email and Networking Tools - IPAddress.com
You get the best results with IPAddress.com’s IP Address Lookup, WHOIS, Email Tracing, Networking Tools and much more!
IPAddress.com

And add ip to your hosts:

vi /etc/hosts
199.232.96.133 raw.githubusercontent.com

Get your secret becore your installation

Find it from you dns provider

export Ali_Key="**********"
export Ali_Secret="**********"
acme.sh --issue --dns dns_ali -d ourdark.org -d *.ourdark.org
acmesh-official/acme.sh
A pure Unix shell script implementing ACME client protocol - acmesh-official/acme.sh
GitHubacmesh-official

Install cert to nginx

mkdir /etc/nginx/ssl
acme.sh --installcert -d ourdark.org \
             --keypath       /etc/nginx/ssl/ourdark.org.key  \
             --fullchainpath /etc/nginx/ssl/ourdark.org.key.pem \
             --reloadcmd     "systemctl restart nginx"

Generate dhparam.pem

It will take some time

openssl dhparam -out /etc/nginx/ssl/dhparam.pem 2048

Update your nginx config

ssl_certificate     /etc/nginx/ssl/ourdark.org.key.pem; 
ssl_certificate_key /etc/nginx/ssl/ourdark.org.key;

then reload your nginx

systemctl restart nginx

Now, you can verify your site: https://blog.ourdark.org

Finally, you should update certs in every 3 months, it's simple

acme.sh --upgrade --auto-upgrade

Renew the cert after 60 days

./acme.sh --renew -d ourdark.com -d *.ourdark.com