func containsDotFile(name string) bool {
	parts := strings.Split(name, "/")
	for _, part := range parts {
		if strings.HasPrefix(part, ".") {
			return true
		}
	}
	return false
}
containsDotFile reports whether name contains a path element starting with a period.
The name is assumed to be a delimited by forward slashes, as guaranteed
by the http.FileSystem interface.
package main
import (
	"net/http"
	"os"
	"strings"
)