fix: secret file reading

[ChristopherHX]

• do ToUpper for keys not only for cli args

Closes #42

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ EDITORCONFIG	editorconfig-checker	2		0	0.01s
✅ REPOSITORY	gitleaks	yes		no	2.72s
✅ REPOSITORY	git_diff	yes		no	0.01s
✅ REPOSITORY	grype	yes		no	9.82s
✅ REPOSITORY	secretlint	yes		no	1.2s
✅ REPOSITORY	trivy-sbom	yes		no	0.1s
✅ REPOSITORY	trufflehog	yes		no	4.46s

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[codecov]

Codecov Report

Attention: Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cmd/root.go	62.50%	3 Missing ⚠️

Files with missing lines	Coverage Δ
cmd/root.go	3.01% <62.50%> (ø)