readme: add openssl cli

README.md

@@ -17,3 +17,29 @@ PublicKeyAlgo  : ECDSA
 "*.foo.balki.me"
 "E7"
 ```
+
+### Use without installing
+
+```
+go run go.balki.me/certinfo@latest foo.crt
+```
+
+```
+podman run -v $PWD:/w -w /w --rm golang go run go.balki.me/certinfo@latest foo.crt
+```
+
+```
+docker run -v $PWD:/w -w /w --rm golang go run go.balki.me/certinfo@latest foo.crt
+```
+
+---
+
+Prefer to use the ugly openssl CLI instead ?
+
+```
+openssl x509 -in foo.crt -text -noout
+```
+
+```
+podman run -v $PWD:/w -w /w --rm archlinux openssl x509 -in foo.crt -text -noout
+```