Update go version (1.16)

[dc7303]

What this PR does / why we need it:
We recommend the latest version of Go, so we will update it.

Which issue(s) this PR fixes:

Fixes #157

Special notes for your reviewer:
Since ioutil is deprecated, I modified the code that uses that package.
https://golang.org/doc/go1.16#ioutil

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Merging #161 (9f810d1) into main (b24df02) will increase coverage by 1.26%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #161      +/-   ##
==========================================
+ Coverage   57.48%   58.75%   +1.26%     
==========================================
  Files          37       37              
  Lines        3262     3280      +18     
==========================================
+ Hits         1875     1927      +52     
+ Misses       1202     1166      -36     
- Partials      185      187       +2     

Impacted Files	Coverage Δ
yorkie/config.go	81.25% <100.00%> (ø)
api/converter/from_pb.go	67.10% <0.00%> (-0.19%)	⬇️
api/converter/to_pb.go	85.65% <0.00%> (+0.11%)	⬆️
pkg/document/json/primitive.go	62.79% <0.00%> (+34.58%)	⬆️

---

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[hackerwins]

@dc7303 Thanks for the contribution. I have a question.
Do we have to update Go version in README.md?

[dc7303]

@hackerwins That's a good point!
We need 1.16 or higher as we change ioutil to io package. So, REAMDE.md update is also required.

But before proceeding with the update, I would like to make a suggestion.
Since the minimum go version is specified in go.mod, how about removing the go version information from REAMDE.md?

[hackerwins]

@dc7303
Thanks for the comments. I think you gave me a suggestion because of the idea that it is redundant.
However, I think it's okay to specify the version as it is easy for new developers to get started. If it's still a problem the next time the Go version is updated, it might be okay to remove it.

[dc7303]

@hackerwins
Thanks for your good opinion! 😄
The README.md has been updated, and the configuration files in workflows have also been updated.

[hackerwins]

LGTM.