[ISSUE #698] fix: call cancel() as soon as possible to release the resources associatd with context

[fengberlin]

Although the the resources associatd with the context created by context.WithTimeout will be release after the timer elapsed, but call cancel() to release the resources as soon as possible can avoid context/memory leak.

[codecov-commenter]

Codecov Report

Merging #691 (506e50e) into master (c688c19) will increase coverage by 0.02%.
The diff coverage is 35.29%.

@@            Coverage Diff             @@
##           master     #691      +/-   ##
==========================================
+ Coverage   24.71%   24.74%   +0.02%     
==========================================
  Files          48       48              
  Lines        5223     5234      +11     
==========================================
+ Hits         1291     1295       +4     
- Misses       3726     3733       +7     
  Partials      206      206              

Impacted Files	Coverage Δ
internal/client.go	0.00% <0.00%> (ø)
internal/trace.go	29.49% <0.00%> (-0.11%)	⬇️
internal/route.go	9.86% <100.00%> (+0.61%)	⬆️
producer/producer.go	28.57% <100.00%> (+0.44%)	⬆️

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[wenfengwang]

It seems that the changes of this PR included in #692

could you separate them or close this PR?

@fengberlin

[fengberlin]

ok. I will separate them in #692. Could you accept this PR first?
@wenfengwang

[fengberlin]

this PR can be remove the duplicate label?
@wenfengwang

[fengberlin]

Please continue reviewing my PR. Thanks.
@wenfengwang

[wenfengwang]

LGTM @ding @maixiaohai

[maixiaohai]

@fengberlin plz create a related issue~

[fengberlin]

@fengberlin plz create a related issue~

I have been created the issue #698 related to this PR.
Plz continue review my PR. Thanks.
@maixiaohai