## itoabase

### Instructions

Write a function that:

- converts an `int` value to a `string` using the specified base in the argument
- and that returns this `string`

The base is expressed as an `int`, from 2 to 16. The characters comprising
the base are the digits from 0 to 9, followed by uppercase letters from A to F.

For example, the base `4` would be the equivalent of "0123" and the base `16` would be the equivalent of "0123456789ABCDEF".

If the value is negative, the resulting `string` has to be preceded by a
minus sign `-`.

Only valid inputs will be tested.

### Expected function

```go
func ItoaBase(value, base int) string {

}
```
