This is a simple program to generate and print the binary reflected Gray code for n-digits. Supply "n" as the single argument when calling the program.

bin-reflected-graycode.go

package main

import (
	"fmt"
	"log"
	"os"
	"strconv"
)

func grayCode(seed []string, len int) []string {
	if len <= 1 {
		return seed
	}
	rev := reverse(seed, 0)
	var a, b []string
	for i := range seed {
		a = append(a, "0"+seed[i])
		b = append(b, "1"+rev[i])
	}
	code := append(reverse(a, 0), b...)
	return grayCode(code, len-1)
}

func reverse(s []string, start int) []string {
	for end := len(s) - 1; start < end; start, end = start+1, end-1 {
		s[start], s[end] = s[end], s[start]
	}
	return s
}

func main() {
	if len(os.Args) < 2 {
		log.Fatal("Invalid usage.")
	}
	n, err := strconv.Atoi(os.Args[1])
	if err != nil {
		log.Fatal("%T: %v", err, err)
	}
	if n == 0 {
		log.Fatal("Integer must be greater than zero.")
	}

	seed := []string{"0", "1"}
	code := grayCode(seed, n)
	for _, v := range code {
		fmt.Println(v)
	}
}