log.go
func SetLogger(out io.Writer, prefix string, flag int) {
	Log = stdlog.New(out, prefix, flag)
}
func SetLogger(out io.Writer, prefix string, flag int) {
	Log = stdlog.New(out, prefix, flag)
}
// SetLogger replaces the default logger with a new
// one that writes to 'out', has 'prefix', and flags 'flag'