I am trying to traverse the file structure in Breadth first fashion. I am getting segmentation violation - go

Question

I know about ioutil.ReadDir and os.filePath but none of them traverse the directory in Breadth first fashion.
My approach is to call ioutil.ReadDir and append all the contents of the root dir into a slice. Then I am iterating over the contents and checking if it IsDir[] and calling the function recursively if true.
package main
import (
"io/ioutil"
"os"
)
var files []string
var path string
func appendFiles(root string) {
fileInfo, err := ioutil.ReadDir(root)
if err != nil {
return
}
for _, file := range fileInfo {
files = append(files, file.Name())
}
for _, file := range fileInfo {
fileStat, _ := os.Stat(file.Name())
if fileStat.Mode().IsDir() {
// path = path + "/" + file.Name()
appendFiles(file.Name())
}
}
}
func main() {
appendFiles(".")
}

Answer 1

The problem is that os.Stat() may return an error which you omit. When that happens, fileStat may be nil, so calling fileStat.Mode() in the next line panics.
And the reason os.Stat() fails is because file.Name() is relative to root, file.Name() by itself has little chance to exist, it must be joined with root. If os.Stat() is called with a file name that doesn't exist, it returns a nil file info and a non-nil error.
You may use filepath.Join() to construct a valid path for files that os.Stat() will work with. And it would be better to handle errors, e.g. return them, which you can inspect in main().
func appendFiles(root string) error {
fileInfo, err := ioutil.ReadDir(root)
if err != nil {
return fmt.Errorf("ReadDir error: %w", err)
}
for _, file := range fileInfo {
files = append(files, filepath.Join(root, file.Name()))
}
for _, file := range fileInfo {
fullName := filepath.Join(root, file.Name())
fileStat, err := os.Stat(fullName)
if err != nil {
return fmt.Errorf("Stat error: %w", err)
}
if fileStat.Mode().IsDir() {
if err := appendFiles(fullName); err != nil {
return fmt.Errorf("appendFiles error: %w", err)
}
}
}
return nil
}
func main() {
if err := appendFiles("."); err != nil {
fmt.Println(err)
}
}