public/subjects/fromto/README.md

## fromto

### Instructions

Write a function that takes two `integers` and returns a `string` showing the range of numbers from the first to the second.

- The numbers must be separated by a comma and a space.
- If any of the arguments is bigger than `99` or less than `0`, the function returns `Invalid` followed by a newline `\n`.
- Prepend a `0` to any number that is less than `10`.
- Add a new line `\n` at the end of the `string`.

### Expected function

```go
func FromTo(from int, to int) string {

}
```

### Usage

Here is a possible program to test your function:

```go
package main

import (
	"fmt"
)

func main() {
	fmt.Print(FromTo(1, 10))
	fmt.Print(FromTo(10, 1))
	fmt.Print(FromTo(10, 10))
	fmt.Print(FromTo(100, 10))
}
```

And its output:

```console
$ go run . | cat -e
01, 02, 03, 04, 05, 06, 07, 08, 09, 10$
10, 09, 08, 07, 06, 05, 04, 03, 02, 01$
10$
Invalid$
```