Update nruneprog.en.md

subjects/nruneprog.en.md

@@ -22,3 +22,43 @@ func NRune(s string, n int) rune {
 
 }
 ```
+### Instructions
+
+Write a function that returns the nth `rune` of a `string`.
+
+### Expected function
+
+```go
+func NRune(s string, n int) rune {
+
+}
+```
+
+### Usage
+
+Here is a possible [program](TODO-LINK) to test your function :
+
+```go
+package main
+
+import (
+	"github.com/01-edu/z01"
+	piscine ".."
+)
+
+func main() {
+	z01.PrintRune(piscine.NRune("Hello!", 3))
+	z01.PrintRune(piscine.NRune("Salut!", 2))
+	z01.PrintRune(piscine.NRune("Ola!", 4))
+	z01.PrintRune('\n')
+}
+```
+
+And its output :
+
+```console
+student@ubuntu:~/piscine-go/test$ go build
+student@ubuntu:~/piscine-go/test$ ./test
+la!
+student@ubuntu:~/piscine-go/test$
+```