update readme

README.md

@@ -10,6 +10,17 @@ Download precompiled [Releases](https://github.com/ffay/lanproxy/releases).
 ```
 > eg: nohup ./client_darwin_amd64 -s lp.thingsglobal.org -p 4900 -k 01c1e176d6ee466c8db717a8 &
 
+```shell
+GLOBAL OPTIONS:
+   -k value       client key
+   -s value       proxy server host
+   -p value       proxy server port (default: 4900)
+   --ssl value    enable ssl (default: "false", -p value should be server ssl port)
+   --cer value    ssl cert path, default skip verify certificate
+   --help, -h     show help
+   --version, -v  print the version
+```
+
 ### Install from source
 
 ```