StatusUpgradeRequired              = 426 // RFC 9110, 15.5.22
	StatusPreconditionRequired         = 428 // RFC 6585, 3
	StatusTooManyRequests              = 429 // RFC 6585, 4
	StatusRequestHeaderFieldsTooLarge  = 431 // RFC 6585, 5
	StatusUnavailableForLegalReasons   = 451 // RFC 7725, 3

	StatusInternalServerError           = 500 // RFC 9110, 15.6.1
	StatusNotImplemented                = 501 // RFC 9110, 15.6.2

pkg net/http, const StatusPreconditionRequired = 428
pkg net/http, const StatusPreconditionRequired ideal-int
pkg net/http, const StatusRequestHeaderFieldsTooLarge = 431
pkg net/http, const StatusRequestHeaderFieldsTooLarge ideal-int
pkg net/http, const StatusTooManyRequests = 429
pkg net/http, const StatusTooManyRequests ideal-int
pkg net/http, const StatusUnavailableForLegalReasons = 451

	"Precondition Required":           http.StatusPreconditionRequired,
	"Too Many Requests":               http.StatusTooManyRequests,
	"Request Header Fields Too Large": http.StatusRequestHeaderFieldsTooLarge,
	"Unavailable For Legal Reasons":   http.StatusUnavailableForLegalReasons,
	"Internal Server Error":           http.StatusInternalServerError,
	"Not Implemented":                 http.StatusNotImplemented,

	// .. "A server that receives a larger header block than it is
	// willing to handle can send an HTTP 431 (Request Header Fields Too
	// Large) status code"
	const statusRequestHeaderFieldsTooLarge = 431 // only in Go 1.6+
	w.WriteHeader(statusRequestHeaderFieldsTooLarge)
	io.WriteString(w, "<h1>HTTP Error 431</h1><p>Request Header Field(s) Too Large</p>")
}

// called from handler goroutines.
// h may be nil.

		{"StatusPreconditionRequired", Const, 6},
		{"StatusProcessing", Const, 7},
		{"StatusProxyAuthRequired", Const, 0},
		{"StatusRequestEntityTooLarge", Const, 0},
		{"StatusRequestHeaderFieldsTooLarge", Const, 6},
		{"StatusRequestTimeout", Const, 0},
		{"StatusRequestURITooLong", Const, 0},
		{"StatusRequestedRangeNotSatisfiable", Const, 0},
		{"StatusResetContent", Const, 0},