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/assign @lyyyuna

Codecov Report

Merging #173 (120ffa3) into master (42f0dfc) will increase coverage by 0.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #173      +/-   ##
==========================================
+ Coverage   67.77%   68.00%   +0.23%     
==========================================
  Files          34       34              
  Lines        1738     1738              
==========================================
+ Hits         1178     1182       +4     
+ Misses        454      451       -3     
+ Partials      106      105       -1     

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注意到我们有自己的 signal notify，这种行为会导致用户原有的一些退出逻辑被破坏：
比如用户原程序注册 signal notify，执行时长为 10s 的清理任务再退出，这时候 goc 注入的 notify 立马 os.Exit() 会直接打断这一行为。

signal handler 目前我想到的分两种情况：

1. go 的 signal notify。看文档允许多个 channel 对应同一个 singnal (https://golang.org/pkg/os/signal/#Notify)
2. linux c 的 signal handler，和 go 抽象过的不同，只能一个。

这部分有必要重新设计。

@lyyyuna 出个方案，我们一起讨论下。

看起来没有更好的方案，先合并以修复问题。