const golang.org/x/sys/unix.SYS_PSYNCH_RW_DOWNGRADE

one use

	golang.org/x/sys/unix (current package)
		zsysnum_darwin_arm64.go#L223: 	SYS_PSYNCH_RW_DOWNGRADE            = 299

The pages are generated with Golds v0.2.8-preview. (GOOS=darwin GOARCH=arm64)