func formatHeader(buf *[]byte, t time.Time, lvl, tag string, file string, line int) {
	year, month, day := t.Date()
	hour, min, sec := t.Clock()
	ms := t.Nanosecond() / 1e6

	itoa(buf, year, 4)
	*buf = append(*buf, '-')
	itoa(buf, int(month), 2)
	*buf = append(*buf, '-')
	itoa(buf, day, 2)
	*buf = append(*buf, ' ')
	itoa(buf, hour, 2)
	*buf = append(*buf, ':')
	itoa(buf, min, 2)
	*buf = append(*buf, ':')
	itoa(buf, sec, 2)
	*buf = append(*buf, '.')
	itoa(buf, ms, 3)
	*buf = append(*buf, " ["...)
	*buf = append(*buf, lvl...)
	*buf = append(*buf, "] "...)
	*buf = append(*buf, tag...)
	if file != "" {
		*buf = append(*buf, ' ')
		*buf = append(*buf, file...)
		*buf = append(*buf, ':')
		itoa(buf, line, -1)
	}
	*buf = append(*buf, ": "...)
}
func formatHeader(buf *[]byte, t time.Time, lvl, tag string, file string, line int) {
	year, month, day := t.Date()
	hour, min, sec := t.Clock()
	ms := t.Nanosecond() / 1e6

	itoa(buf, year, 4)
	*buf = append(*buf, '-')
	itoa(buf, int(month), 2)
	*buf = append(*buf, '-')
	itoa(buf, day, 2)
	*buf = append(*buf, ' ')
	itoa(buf, hour, 2)
	*buf = append(*buf, ':')
	itoa(buf, min, 2)
	*buf = append(*buf, ':')
	itoa(buf, sec, 2)
	*buf = append(*buf, '.')
	itoa(buf, ms, 3)
	*buf = append(*buf, " ["...)
	*buf = append(*buf, lvl...)
	*buf = append(*buf, "] "...)
	*buf = append(*buf, tag...)
	if file != "" {
		*buf = append(*buf, ' ')
		*buf = append(*buf, file...)
		*buf = append(*buf, ':')
		itoa(buf, line, -1)
	}
	*buf = append(*buf, ": "...)
}
func formatHeader ( buf * [ ] byte , t time . Time , lvl , tag string , file string , line int ) { year , month , day := t . Date ( ) hour , min , sec := t . Clock ( ) ms := t . Nanosecond ( ) / 1e6 itoa ( buf , year , 4 ) * buf = append ( * buf , '-' ) itoa ( buf , int ( month ) , 2 ) * buf = append ( * buf , '-' ) itoa ( buf , day , 2 ) * buf = append ( * buf , ' ' ) itoa ( buf , hour , 2 ) * buf = append ( * buf , ':' ) itoa ( buf , min , 2 ) * buf = append ( * buf , ':' ) itoa ( buf , sec , 2 ) * buf = append ( * buf , '.' ) itoa ( buf , ms , 3 ) * buf = append ( * buf , " " ... ) * buf = append ( * buf , lvl ... ) * buf = append ( * buf , " " ... ) * buf = append ( * buf , tag ... ) if file != " " { * buf = append ( * buf , ' ' ) * buf = append ( * buf , file ... ) * buf = append ( * buf , ':' ) itoa ( buf , line , - 1 ) } * buf = append ( * buf , " " ... ) }
// Appends a header in the default format 'YYYY-MM-DD hh:mm:ss.sss [LVL] TAG: '.
// If either of the Lshortfile or Llongfile flags are specified, the file named
// and line number are included after the tag and before the final colon.
Appends a header in the default format YYYY - MM - DD hh : mm : ss . sss [ LVL ] TAG : . If either of the Lshortfile or Llongfile flags are specified the file named and line number are included after the tag and before the final colon .