func PrivateKeyFromFile(password, path string) (PrivateKey, error) {
	bytes, err := ioutil.ReadFile(path)
	if err != nil {
		return PrivateKey{}, err
	}
	return DecryptKey(password, bytes)
}
PrivateKeyFromFile reads and decrypts the private key
file with the given password.
package minisign
import (
	"crypto"
	"crypto/ed25519"
	"crypto/rand"
	"crypto/subtle"
	"encoding/base64"
	"encoding/binary"
	"errors"
	"io"
	"io/ioutil"
	"strconv"
	"strings"
	"time"
	"golang.org/x/crypto/blake2b"
	"golang.org/x/crypto/scrypt"
)