"x-forwarded-for",
		"x-forwarded-proto",
	}
	http2commonLowerHeader = make(map[string]string, len(common))
	http2commonCanonHeader = make(map[string]string, len(common))
	for _, v := range common {
		chk := CanonicalHeaderKey(v)
		http2commonLowerHeader[chk] = v
		http2commonCanonHeader[v] = chk
	}
}

func http2lowerHeader(v string) (lower string, ascii bool) {
	http2buildCommonHeaderMapsOnce()