fix graceful shutdwon add sigterm signal

[relaxedCat]

No description provided.

[codecov-commenter]

Codecov Report

Merging #657 into develop will decrease coverage by 0.07%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #657      +/-   ##
===========================================
- Coverage    63.87%   63.80%   -0.08%     
===========================================
  Files          236      236              
  Lines        12313    12313              
===========================================
- Hits          7865     7856       -9     
- Misses        3677     3690      +13     
+ Partials       771      767       -4     

Impacted Files	Coverage Δ
metadata/report/delegate/delegate_report.go	29.41% <0.00%> (-9.56%)	⬇️
protocol/dubbo/client.go	69.09% <0.00%> (+1.21%)	⬆️
cluster/cluster_impl/failback_cluster_invoker.go	80.21% <0.00%> (+2.19%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8347779...d3db1c2. Read the comment docs.