OpenBSD is removing the syscall(2) interface soon and ioctl operations using
syscall.Syscall6 will fail to link at runtime:
$ go test
tmpdir: /tmp
readline.test:/tmp/go-build2875288623/b001/readline.test: undefined symbol 'syscall'
ld.so: readline.test: lazy binding failed!
signal: killed
FAIL github.com/chzyer/readline 0.008s
These calls must instead be performed using the golang.org/x/sys/unix package,
which links to the ioctl(2) libc stub instead of the generic syscall(2)
interface.