[BUG] [Go] Generated client code does not pass golint and has several style antipatterns

Created by: aeneasr

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
Have you tested with the latest master to confirm the issue still exists?
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Description

Generating a Go client generates code which does not pass golint. Passing golint checks is important because it can detect Go anti-patterns. I listed some of the output below

api_health.go:27:6: type `HealthApiService` should be `HealthAPIService` (golint)
type HealthApiService service
     ^
api_public.go:1270:2: don't use underscores in Go names; struct field error_ should be error (golint)
        error_ *string
        ^
api_public.go:1273:49: don't use underscores in Go names; method Error_ should be Error (golint)
func (r PublicApiApiGetSelfServiceErrorRequest) Error_(error_ string) PublicApiApiGetSelfServiceErrorRequest {
                                                ^

errcheck is not golint but detects missing error checks:

client.go:245:18: Error return value of `w.WriteField` is not checked (errcheck)
                                        w.WriteField(k, iv)
                                                    ^

client.go:115:6: SA6005: should use strings.EqualFold instead (staticcheck)
                if strings.ToLower(a) == strings.ToLower(needle) {
                   ^

Other code-"smells" not detected by golint or golangci-lint are:

non-nilable errors #8483 (closed)
Abbreviated names are not capitalized (struct{ Id string `json:"id"` }) but should be (e.g. struct {ID string `json:"id"`})
Slice fields are referenced as pointers (struct Foo { Bar *[]Bar }) but should be referenced as regular slices (e.g. struct Foo { Bar []Bar }.

openapi-generator version

5.0.0

OpenAPI declaration file content or url

Any valid OpenAPI 3.0 schema.

Generation Details

npm run openapi-generator-cli -- generate -i ".schema/api.openapi.json" \
				-g go \
				-o "internal/httpclient" \
				--git-user-id ory \
				--git-repo-id kratos-client-go \
				--git-host github.com \
				-c .schema/openapi/gen.go.yml

Steps to reproduce

See above