func SHA1sum(filename string) (string, error) {
	return sum(sha1.New(), filename)
}
SHA1sum returns SHA1 checksum of filename
package checksum
import (
	"bufio"
	"crypto/md5"
	"crypto/sha1"
	"crypto/sha256"
	"hash"
	"os"
)
func MD5sum(filename string) (string, error) {
	return sum(md5.New(), filename)
}
func SHA256sum(filename string) (string, error) {
	return sum(sha256.New(), filename)
}