func (pe *ProtocolError) Is(err error) bool {
	return pe == ErrNotSupported && err == errors.ErrUnsupported
}

var (
	// ErrNotSupported indicates that a feature is not supported.
	//
	// It is returned by ResponseController methods to indicate that
	// the handler does not support the method, and by the Push method
	// of Pusher implementations to indicate that HTTP/2 Push support
	// is not available.

		{"(*Response).ProtoAtLeast", Method, 0},
		{"(*Response).Write", Method, 0},
		{"(*ResponseController).EnableFullDuplex", Method, 21},
		{"(*ResponseController).Flush", Method, 20},
		{"(*ResponseController).Hijack", Method, 20},
		{"(*ResponseController).SetReadDeadline", Method, 20},
		{"(*ResponseController).SetWriteDeadline", Method, 20},
		{"(*ServeMux).Handle", Method, 0},
		{"(*ServeMux).HandleFunc", Method, 0},

	// can deadlock if we start writing the response with unconsumed body
	// remaining. See Issue 15527 for some history.
	//
	// If full duplex mode has been enabled with ResponseController.EnableFullDuplex,
	// then leave the request body alone.
	//
	// We don't take this path when w.closeAfterReply is set.
	// We may not need to consume the request to get ready for the next one