Added code for recursively traversing directories

kg/main.go

@@ -5,7 +5,9 @@ import (
 	"flag"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
+	"path/filepath"
 	"slices"
 
 	"github.com/fatih/color"
@@ -101,7 +103,24 @@ func main() {
 					os.Exit(2)
 				} else {
 					if fileStat.Mode().IsDir() {
-						fmt.Printf("%s: %s: Is a directory\n", os.Args[0], inputFilename)
+						if *recursiveFlag {
+							// Walk the directory and open every file in it. Add each file to the filelist.
+							filepath.WalkDir(inputFilename, func(filename string, d fs.DirEntry, err error) error {
+								if err != nil {
+									return err
+								}
+								if !d.IsDir() {
+									f, err := os.Open(filename)
+									if err != nil {
+										return err
+									}
+									inputFiles = append(inputFiles, f)
+								}
+								return nil
+							})
+						} else {
+							fmt.Printf("%s: %s: Is a directory\n", os.Args[0], inputFilename)
+						}
 					} else {
 						var nullCharPresent bool
 						if nullCharPresent, err = fileContainsNullChar(inputFilename); nullCharPresent {