## islower

### Instructions

Write a function that returns 'true' if the 'string' passed as the parameter contains only lowercase characters; returns 'false' otherwise.

### Expected function

```go
func IsLower(s string) bool {

}
```

### Usage

Here is a possible program to test your function :

```go
package main

import (
	"fmt"
	"piscine"
)

func main() {
	fmt.Println(piscine.IsLower("hello"))
	fmt.Println(piscine.IsLower("hello!"))

}
```

And its output :

```console
$ go run .
true
false
$
```