from the 1.22 release notes:
The syscall package has been frozen since Go 1.4 and was marked as deprecated in Go 1.11 [...]
However, some non-deprecated functionality requires use of the syscall package [...]
To avoid unnecessary complaints[...] no longer marked as deprecated.
The package remains frozen to most new functionality, and new code remains encouraged
to use golang.org/x/sys/unix or golang.org/x/sys/windows where possible.