通过环境变量支持自定义service name

[williamfzc]

见 #199 #292

/assign @memoryliu
/approve

[codecov]

Codecov Report

Merging #293 (bc5f609) into master (50b62f0) will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #293      +/-   ##
==========================================
- Coverage   70.85%   70.76%   -0.10%     
==========================================
  Files          34       34              
  Lines        2035     2035              
==========================================
- Hits         1442     1440       -2     
- Misses        480      482       +2     
  Partials      113      113              

Flag	Coverage Δ
e2e-1.16.x	?
e2e-1.17.x	?
e2e-1.18.x	?
unittest-1.16.x	70.66% <ø> (-0.20%)	⬇️
unittest-1.17.x	70.76% <ø> (+0.09%)	⬆️
unittest-1.18.x	70.66% <ø> (-0.20%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/cover/instrument.go	20.83% <ø> (ø)
pkg/build/gomodules.go	89.18% <0.00%> (-5.41%)	⬇️

[CarlJi]

Thanks for your contribution @williamfzc

I am thinking that it's better to provide some explanations for this enhancement. And here seems a proper place. Of course, you can submit another PR if you will.

Thanks again.

[CarlJi]

/lgtm
/approve

[qiniu-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CarlJi, williamfzc

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