httpclient/http.go
func copyHiddenHeaders(from map[string]bool) (to map[string]bool) {
	to = make(map[string]bool)
	for k, v := range from {
		to[k] = v
	}
	return
}
func copyHiddenHeaders(from map[string]bool) (to map[string]bool) {
	to = make(map[string]bool)
	for k, v := range from {
		to[k] = v
	}
	return
}
// copyHiddenHeaders copies the given map