use specific errors with exit codes

main.go

@@ -9,6 +9,17 @@ import (
 func main() {
 	rootCmd := cmd.NewRootCommand()
 	if err := rootCmd.Execute(); err != nil {
-		os.Exit(1)
+		switch err.(type) {
+		case cmd.ValidationError:
+			os.Exit(1)
+		case cmd.ArgumentError:
+			os.Exit(2)
+		case cmd.InternalError:
+			os.Exit(3)
+		default:
+			// This case should not get hit, but in case it does,
+			// Treat unknown error as internal error
+			os.Exit(3)
+		}
 	}
 }

pkg/cmd/errors.go

@@ -0,0 +1,7 @@
+package cmd
+
+type ArgumentError error
+
+type ValidationError error
+
+type InternalError error

pkg/cmd/validate.go

@@ -214,12 +214,12 @@ func (c *commandFlags) Run(cmd *cobra.Command, args []string) error {
 		),
 	)
 	if err != nil {
-		return err
+		return ArgumentError(err)
 	}
 
 	files, err := utils.FindFiles(args...)
 	if err != nil {
-		return err
+		return ArgumentError(err)
 	}
 
 	hasError := false
@@ -252,13 +252,13 @@ func (c *commandFlags) Run(cmd *cobra.Command, args []string) error {
 		}
 		data, e := json.MarshalIndent(res, "", "    ")
 		if e != nil {
-			return fmt.Errorf("failed to render results into JSON: %w", e)
+			return InternalError(fmt.Errorf("failed to render results into JSON: %w", e))
 		}
 		fmt.Fprintln(cmd.OutOrStdout(), string(data))
 	}
 
 	if hasError {
-		return errors.New("validation failed")
+		return ValidationError(errors.New("validation failed"))
 	}
 	return nil
 }