Compare bits in two arrays

I've got stuck with ex4.1 for the book which says: <br />
Write a function that counts the number of bits that are different in two SHA256 hashes.

The partial solution I came up with is pasted below, but it's wrong - it counts number of different bytes not bits.
Could you please point me in the right direction?

package main

import (
    "crypto/sha256"
    "fmt"
)

var s1 string = "unodostresquatro"
var s2 string = "UNODOSTRESQUATRO"
var h1 = sha256.Sum256([]byte(s1))
var h2 = sha256.Sum256([]byte(s2))

func main() {
    fmt.Printf("s1: %s h1: %X h1 type: %T\n", s1, h1, h1) 
    fmt.Printf("s2: %s h2: %X h2 type: %T\n", s2, h2, h2) 
    fmt.Printf("Number of different bits: %d\n", 8 * DifferentBits(h1, h2))
}

func DifferentBits(c1 [32]uint8, c2 [32]uint8) int {
    var counter int 
    for x := range c1 {
        if c1[x] != c2[x] {
            counter += 1
        }
    }   
    return counter

}

> The Go Programming Language
>
> Alan A. A. Donovan · Brian W.Kernighan
>
> Exercise 4.1: Write a function that counts the number of bits that
> are different in two SHA256 hashes.

> The C Programming Language
>
> Brian W.Kernighan · Dennis M. Ritchie
>
> Exercise 2-9. In a two's complement number system, x &= (x-1) deletes
> the rightmost 1-bit in x. Use this observation to write a faster
> version of bitcount.

> Bit Twiddling Hacks
>
> Sean Eron Anderson
>
> Counting bits set, Brian Kernighan's way
>
> unsigned int v; // count the number of bits set in v
> unsigned int c; // c accumulates the total bits set in v
> for (c = 0; v; c++)
> {
> v &= v - 1; // clear the least significant bit set
> }

For exercise 4.1, you are counting the number of bytes that are different. Count the number of bits that are different. For example,

package main

import (
	"crypto/sha256"
	"fmt"
)

func BitsDifference(h1, h2 *[sha256.Size]byte) int {
	n := 0
	for i := range h1 {
		for b := h1[i] ^ h2[i]; b != 0; b &= b - 1 {
			n++
		}
	}
	return n
}

func main() {
	s1 := "unodostresquatro"
	s2 := "UNODOSTRESQUATRO"
	h1 := sha256.Sum256([]byte(s1))
	h2 := sha256.Sum256([]byte(s2))
	fmt.Println(BitsDifference(&h1, &h2))
}

Output:

139

Here is how I would do it

package main

import (
	"crypto/sha256"
	"fmt"
)

var (
	s1 string = "unodostresquatro"
	s2 string = "UNODOSTRESQUATRO"
	h1        = sha256.Sum256([]byte(s1))
	h2        = sha256.Sum256([]byte(s2))
)

func main() {
	fmt.Printf("s1: %s h1: %X h1 type: %T\n", s1, h1, h1)
	fmt.Printf("s2: %s h2: %X h2 type: %T\n", s2, h2, h2)
	fmt.Printf("Number of different bits: %d\n", DifferentBits(h1, h2))
}

// bitCount counts the number of bits set in x
func bitCount(x uint8) int {
	count := 0
	for x != 0 {
		x &= x - 1
		count++
	}
	return count
}

func DifferentBits(c1 [32]uint8, c2 [32]uint8) int {
	var counter int
	for x := range c1 {
		counter += bitCount(c1[x] ^ c2[x])
	}
	return counter
}

Playground