remove depguard and fix linter warnings

.golangci.yml

@@ -6,7 +6,6 @@ linters:
     - decorder
     - containedctx
     - contextcheck
-    - depguard
     - dogsled
     - dupl
     - errcheck

f2_test/f2_unix_test.go

@@ -6,7 +6,7 @@ package f2_test
 import "testing"
 
 // dummy function necessary for compilation in Unix.
-func setHidden(path string) error {
+func setHidden(_ string) error {
 	return nil
 }
 

find/find_unix.go

@@ -6,6 +6,6 @@ package find
 // isHidden checks if a file is hidden on Unix operating systems
 // the nil error is returned to match the signature of the Windows
 // version of the function.
-func isHidden(filename, baseDir string) (bool, error) {
+func isHidden(filename, _ string) (bool, error) {
 	return filename[0] == dotCharacter, nil
 }