Refactored code structure

src/errors/UnusedVariable.go

@@ -1,13 +0,0 @@
-package errors
-
-import "fmt"
-
-// UnusedVariable error is created when a defined variable is never used.
-type UnusedVariable struct {
-	Name string
-}
-
-// Error generates the string representation.
-func (err *UnusedVariable) Error() string {
-	return fmt.Sprintf("Unused variable '%s'", err.Name)
-}