Comparing elements of two string slices in golang

comparer.go

// You can test here: https://play.golang.org/p/zTaNla0oXJ
package main

import (
	"fmt"
)

func main() {
	x := []string{"a","b","c"}
	y := []string{"c", "d"}
	//z := []string{"c", "d"}
	w := compare(y, x)
	fmt.Println(w)
}

func compare(a, b []string) []string {
	for i := len(a) - 1; i >= 0; i-- {
		for _, vD := range b {
			if a[i] == vD {
				a = append(a[:i], a[i+1:]...)
				break
			}
		}
	}
	return a
}