treewide: run gofmt -s and enable linter

Change-Id: I90b8ef48c955dccfddc5bbc0a57205b7da844b60
Reviewed-on: https://review.monogon.dev/c/monogon/+/3828
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/osbase/pki/certificate.go b/osbase/pki/certificate.go
index b925958..93e6ed9 100644
--- a/osbase/pki/certificate.go
+++ b/osbase/pki/certificate.go
@@ -115,7 +115,8 @@
 
 // Client makes a Kubernetes PKI-compatible client certificate template.
 // Directly derived from Kubernetes PKI requirements documented at
-//   https://kubernetes.io/docs/setup/best-practices/certificates/#configure-certificates-manually
+//
+//	https://kubernetes.io/docs/setup/best-practices/certificates/#configure-certificates-manually
 func Client(identity string, groups []string) x509.Certificate {
 	return x509.Certificate{
 		Subject: pkix.Name{