Use camel case instead of ALL_CAPS

[crispgm]

ENV_GIN_MODE -> EnvGinMode

[codecov]

Codecov Report

Merging #1419 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1419   +/-   ##
=======================================
  Coverage   98.48%   98.48%           
=======================================
  Files          41       41           
  Lines        2049     2049           
=======================================
  Hits         2018     2018           
  Misses         19       19           
  Partials       12       12

Impacted Files	Coverage Δ
mode.go	90.9% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 48f6c61...7e9d93e. Read the comment docs.

[thinkerou]

it will break forward compatibility.

[crispgm]

@thinkerou well, should I close?

[thinkerou]

@crispgm sorry, I understand error, it not break, because set environment var using GIN_MODE, so not close, need cr, thanks!

[thinkerou]

@crispgm maybe we should use ALL_CAPS for const, https://github.com/Unknwon/go-code-convention/blob/master/en-US/naming_rules.md#constants, but I not find the official document.

[crispgm]

@thinkerou Nope, mixed caps is the common practice for constants, which is used by go linters.
See https://github.com/golang/go/wiki/CodeReviewComments#mixed-caps.
And this is what we do in other packages. :)