fix(): ringfd close

Signed-off-by: MastahSenpai <26342994+ii64@users.noreply.github.com>

core.go

@@ -1,6 +1,8 @@
 package gouring
 
 import (
+	"syscall"
+
 	"github.com/pkg/errors"
 )
 
@@ -22,6 +24,11 @@ func (r *Ring) Close() (err error) {
 		err = errors.Wrap(err, "close")
 		return
 	}
+
+	if err = syscall.Close(r.fd); err != nil {
+		err = errors.Wrap(err, "close")
+		return
+	}
 	// tbd..
 	return
 }