append config watchers when watch source

[byteneco]

Description (what this PR does / why we need it):

add watchers to config when load.

Which issue(s) this PR fixes:

fixes #1318

Other special notes for reviewer:

[codecov-commenter]

Codecov Report

Merging #1320 (19b5f9c) into main (6ae2e87) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 19b5f9c differs from pull request most recent head 357d1f4. Consider uploading reports for the commit 357d1f4 to get more accurate results

@@            Coverage Diff             @@
##             main    #1320      +/-   ##
==========================================
+ Coverage   54.34%   54.35%   +0.01%     
==========================================
  Files          56       56              
  Lines        2672     2673       +1     
==========================================
+ Hits         1452     1453       +1     
  Misses       1078     1078              
  Partials      142      142              

Impacted Files	Coverage Δ
config/config.go	56.94% <100.00%> (+0.60%)	⬆️

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[byteneco]

#1319
this pr will fix this

[daemon365]

想了下 我那个不适配现有的etcd等 在这讨论下 怎么改吧

[byteneco]

可以返回特定的Error来停止死循环吗