kubectl patch storageclass basic -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

kubectl patch storageclass gp2 -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"false"}}}'
kubectl patch storageclass gp2 -p '{"metadata": {"annotations":{"storageclass.beta.kubernetes.io/is-default-class":"false"}}}'