Sorting/RadixSort [Golang]

#### This issue is about [RadixSort](https://github.com/iiitv/algos/tree/master/radix_sort).

- [x] Issue Title is in form `Algo/DS Name [Language]`.
- [x] I searched or browsed the repo’s other issues to ensure this is not a duplicate.
- [x] This Algo/DS is worth adding to this repository.
- [ ] Assign this issue to me (I want to work on this).
- [ ] I ensure that I am not already assigned to 2 or more issues.
- [x] I will send my PR only after I'm assigned to this issue by any maintainer.
- [x] I understand that I will be unassigned from this issue if I fail to send a PR for this within a week.

Start by reading the linked radix_sort directory and nearby algorithm implementations in the repository to understand its conventions. Add the Go RadixSort implementation in that area, with behavior consistent with the repository’s existing algorithms; completion means the algorithm is present and ready for a maintainer review.

Written by the indexing model from the issue text.