Case insensitive HasSuffix in Go

I am looking for specific file types from a directory listing and use HasSuffix to do the comparision looking for a few specific file types. I would like to make this comparison case insensitive.

Is there a way to add EqualFold or another case insensitive comparison to the HasSuffix function?

You could just use

if strings.HasSuffix(strings.ToLower(s), "suffix") {
	// do something	
}

You can also write your own wrapper function:

func hasSuffix(s, suffix string, caseSensitive bool) bool {
	if caseSensitive {
		return strings.HasSuffix(s, suffix)
	}
	return strings.HasSuffix(strings.ToLower(s), suffix)
}

For file names or paths you can use (see answer of PeterSO):

if strings.ToLower(filepath.Ext(s)) == ".fileending" {
    // do something
}

> "I am looking for specific file types from a directory listing. I would like to make this comparison case insensitive."

For example,

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
)

func hasExts(path string, exts []string) bool {
	pathExt := strings.ToLower(filepath.Ext(path))
	for _, ext := range exts {
		if pathExt == strings.ToLower(ext) {
			return true
		}
	}
	return false
}

func main() {
	dir := `./`
	files, err := ioutil.ReadDir(dir)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		return
	}
	sourceExts := []string{".go", ".Py", ".c", ".cpp"}
	for _, fi := range files {
		if hasExts(fi.Name(), sourceExts) {
			fmt.Println(fi.Name())
		}
	}
}

Output:

t.c
t.go
t.py
t1.go
t1.py
t2.go

For a special form of strings.HasSuffix start by copying the code from the strings package.

func HasSuffix(s, suffix string) bool {
  	return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
}

Then modify it to suit your purpose. For example,

func hasSuffix(s, suffix string) bool {
	return len(s) >= len(suffix) &&
		strings.ToLower(s[len(s)-len(suffix):]) == strings.ToLower(suffix)
}