String seeded random string generator in GO

main.go

package main

import (
	"crypto/sha256"
	"encoding/base64"
	"encoding/binary"
	"fmt"
	"io"
	"math/rand"
)

func getSeededRandomString(seedString string, length int) (string, error) {
	h := sha256.New()
	_, err := io.WriteString(h, seedString)
	if err != nil {
		return "", err
	}
	seed := binary.BigEndian.Uint64(h.Sum(nil))
	fmt.Println(seed)
	myRand := rand.New(rand.NewSource(int64(seed)))
	output := ""
	var buffer []byte
	for len(output) < length {
		buffer = make([]byte, 32)
		_, err = myRand.Read(buffer)
		if err != nil {
			return "", err
		}
		output = output + base64.URLEncoding.EncodeToString(buffer)
	}
	return output[:length], nil
}

func main() {
	output, err := getSeededRandomString("mart2in", 25)
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(output)
}