## alphamirror
### Instructions
Write a program called `alphamirror` that takes a `string` as argument and displays this `string` after replacing each alphabetical character with the opposite alphabetical character.
The case of the letter stays the same, for example :
'a' becomes 'z', 'Z' becomes 'A'
'd' becomes 'w', 'M' becomes 'N'
The final result will be followed by a newline (`'\n'`).
If the number of arguments is different from 1, the program displays only a newline (`'\n'`).
### Usage
```console
student@ubuntu:~/piscine-go/alphamirror$ go build
student@ubuntu:~/piscine-go/alphamirror$ ./alphamirror "abc"
zyx
student@ubuntu:~/piscine-go/alphamirror$ ./alphamirror "My horse is Amazing." | cat -e
Nb slihv rh Znzarmt.$
student@ubuntu:~/piscine-go/alphamirror$ ./alphamirror | cat -e
$
student@ubuntu:~/piscine-go/alphamirror$
```
