[BUG][GO] generated go code not not formatted properly

[Fjolnir-Dvorak]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• • generated sample code in ./samples/client/petstore/go/
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• • branch master date 2019-10-02 commit c136b83
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• • run go fmt on the generated code and view changes via git diff
• [Optional] Bounty to sponsor the fix (example)

Description

The generated code does not follow the go coding standards (go fmt)

openapi-generator version

commit c136b83 (latest commit on master on 2019-10-02T15:27:00)

Steps to reproduce

cd ./samples/client/petstore/go
cd ./go-petstore
go fmt ./*
cd ../go-petstore-withXml
go fmt ./*
cd ../../../../server/petstore/go-gin-api-server
go fmt ./*

Suggest a fix

Correct all mustache templates and add a test for the build servers which runs "go fmt" and checks if there are any changed files. If yes, the test should fail.

[wing328]

You can use file post-processing to format the code using your favorite code formatter.

Run ./bin/go-petstore.sh and you will see the following output:

[main] INFO  o.o.c.languages.AbstractGoCodegen - Environment variable GO_POST_PROCESS_FILE not defined so Go code may not be properly formatted. To define it, try `export GO_POST_PROCESS_FILE="/usr/local/bin/gofmt -w"` (Linux/Mac)
[main] INFO  o.o.c.languages.AbstractGoCodegen - NOTE: To enable file post-processing, 'enablePostProcessFile' must be set to `true` (--enable-post-process-file for CLI).