Add build tag nomsgpack

[sapk]

This PR add a build tag nomsgpack to exclude heavy deps github.com/ugorji/go/codec that may be not needed for most project. The goal is to reduce the resulting binary size. This could maybe improve some performances but that not the goal so I haven't bench it.

I go for the no impact by default by using a negate tag so that without change it will not impact project depending on this lib.

I will try to provide some results of binary size based on https://github.com/gin-gonic/examples. -> see comment

Should fix (or at least a mitigation to) #1847

[codecov]

Codecov Report

Merging #1852 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #1852      +/-   ##
=========================================
+ Coverage   98.49%   98.5%   +0.01%     
=========================================
  Files          40      41       +1     
  Lines        2256    2276      +20     
=========================================
+ Hits         2222    2242      +20     
  Misses         18      18              
  Partials       16      16

Impacted Files	Coverage Δ
binding/msgpack.go	100% <ø> (ø)	⬆️
render/msgpack.go	100% <ø> (ø)	⬆️
render/render.go	100% <ø> (ø)	⬆️
binding/binding.go	100% <ø> (ø)	⬆️
binding/binding_nomsgpack.go	100% <100%> (ø)

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[sapk]

Using the basic example :

go build ./
go build -ldflags="-s -w" -o basic.stripped ./
go build -tags nomsgpack -o basic.nomsgpack ./
go build -tags nomsgpack -ldflags="-s -w" -o basic.nomsgpack.stripped ./
ls -l basic*
-rwxr-xr-x 1 sapk sapk 17129377  9 avril 01:17 basic
-rwxr-xr-x 1 sapk sapk 12749851  9 avril 01:18 basic.nomsgpack
-rwxr-xr-x 1 sapk sapk  9342944  9 avril 01:21 basic.nomsgpack.stripped
-rwxr-xr-x 1 sapk sapk 12755840  9 avril 01:22 basic.stripped

Without the nomsgpack flag the resulting binary file are 35% bigger.

I used go version go1.12.1 linux/amd64 with in go.mod replace github.com/gin-gonic/gin => github.com/sapk-fork/gin v1.3.1-0.20190408225948-e3c972a151c8

[zzjin]

sounds good for ci. any update here?

[appleboy]

@sapk Could you resolve the conflicts?

[sapk]

@lunny done

[lunny]

@sapk :)

[appleboy]

@thinkerou what do you think about this PR?

[sapk]

To re-validate, I re-did the size bench after last rebase.

-rwxr-xr-x 1 sapk sapk 15269181 28 déc.  19:41 basic
-rwxr-xr-x 1 sapk sapk 12925564 28 déc.  19:40 basic.nomsgpack
-rwxr-xr-x 1 sapk sapk  9506816 28 déc.  19:41 basic.nomsgpack.stripped
-rwxr-xr-x 1 sapk sapk 11239424 28 déc.  19:40 basic.stripped

[thinkerou]

1. please update copyright
2. filename: binding_nomsgpack.go binding_msgpack_test.go, should we use xxx_msgpack_xxx?
3. the file and binding.go have repeat code, should we use reduce?
   thanks!

[sapk]

Suggested change

	// Copyright 2014 Manu Martinez-Almeida. All rights reserved.
	// Copyright 2020 Gin Core Team. All rights reserved.

I will have fresh look on removing/refactor duplicate code later.

[appleboy]

maybe need another PR to update documentation.

[sapk]

@lunny for the doc you mean in the README.md ?

[appleboy]

@sapk like as https://github.com/gin-gonic/gin#build-with-jsoniter

[lowang-bh]

I hear that msgpack‘s performance is better than json.

[duaneking]

I'm loving this change and I'm glad it was made because I just did the math and calculated that it will save a company actual money.