support goc version using go get

[lyyyuna]

1. install with go get (auto-version branch has latest code)

$ go get -u github.com/qiniu/goc@auto-version

$ goc version
v1.0.2-0.20200704073344-bc3968fc06bb

2. install/build in local

$ goc version
(devel)

3. binary downloaded in release page, for example:

➜  ~ wget https://github.com/lyyyuna/goc-1/releases/download/v0.9.5/goc-1-v0.9.5-linux-amd64.tar.gz
.....
➜  ~ tar xvf goc-1-v0.9.5-linux-amd64.tar.gz
goc
➜  ~ ./goc version
v0.9.5

[qiniu-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lyyyuna

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Needs approval from an approver in each of these files:

• OWNERS [lyyyuna]

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[codecov]

Codecov Report

Merging #60 into master will decrease coverage by 0.09%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #60      +/-   ##
==========================================
- Coverage   51.13%   51.03%   -0.10%     
==========================================
  Files          32       32              
  Lines        1588     1591       +3     
==========================================
  Hits          812      812              
- Misses        657      660       +3     
  Partials      119      119              

Impacted Files	Coverage Δ
cmd/version.go	25.00% <0.00%> (-15.00%)	⬇️

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[lyyyuna]

/assign @CarlJi

[CarlJi]

/lgtm