Expanded randNum function comments to provide detailed behavior and usage across different Go versions. Enhanced the randomStringSecure function doc to explain its cryptographic secure implementation and error handling.
Removed error handling from `randNum` in `random_test.go` and introduced new `randNum` implementations for different Go versions (1.19, 1.20-1.21, 1.22+). This ensures compatibility with different versions of Go and utilizes the appropriate version-specific random number generation methods. We are using math/rand instead crypto/rand. For our needs this should be sufficient.