默认token的有效期为24小时，当过期之后，该token就不可用了。
产生token:
kubeadm token create
oapcal.mlearjiaijljtyeq
取ca证书sha256编码hash值：
openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'
8832ca46fa644aa8d4864119430985875f27f29bc68dd86797e0b0fa4db60fb4
kubeadm join 192.168.1.130:6443 --token oapcal.mlearjiaijljtyeq --discovery-token-ca-cert-hash sha256:8832ca46fa644aa8d4864119430985875f27f29bc68dd86797e0b0fa4db60fb4
