palindrome.go

package main

import (
        "fmt"
        "unicode"

        "golang.org/x/text/unicode/norm"
)

func main() {
        tests := []struct {
                t   string
                res bool
        }{
                {"", true},
                {"a", true},
                {"A ny你y, na", true},
                {"any你ad", false},
                {"aéa", true},
        }

        for _, tc := range tests {
                if res := isPalindrome(tc.t); res != tc.res {
                        fmt.Printf("[FAIL] for %q got %t; expected %t\n", tc.t, res, tc.res)
                } else {
                        pass := "is"
                        if res == false {
                                pass = "is not"
                        }
                        fmt.Printf("[PASS] %q %s a palindrome\n", tc.t, pass)
                }
        }
}

func isPalindrome(s string) bool {
        t := clean(s)
        l := len(t)
        for i := 0; i < l/2; i++ {
                if t[i] != t[l-i-1] {
                        return false
                }
        }
        return true
}

// remove non-letters and convert to lower case
func clean(s string) []rune {
        t := []rune(string(norm.NFC.Bytes([]byte(s)))) // Normalize and convert to []rune
        c := 0                                         // insert index
        for _, r := range t {
                if unicode.IsLetter(r) {
                        t[c] = unicode.ToLower(r)
                        c++
                }
        }
        return t[:c]
}

Playground link - https://play.golang.org/p/eHY8-zbUAa (does not work in playground).
Output:

[PASS] "" is a palindrome
[PASS] "a" is a palindrome
[PASS] "A ny你y, na" is a palindrome
[PASS] "any你ad" is not a palindrome
[PASS] "aéa" is a palindrome