Add linting

.gitlab-ci.yml

.golangci.yml

Makefile

ekms/api/go/rest/etsi/server/go/api.go

ekms/api/go/rest/etsi/server/go/api_default.go

ekms/api/go/rest/etsi/server/go/api_default_service.go

ekms/api/go/rest/etsi/server/go/error.go

ekms/api/go/rest/etsi/server/go/helpers.go

ekms/api/go/rest/etsi/server/go/impl.go

ekms/api/go/rest/etsi/server/go/model_error_format.go

ekms/api/go/rest/etsi/server/go/model_key_container.go

.../go/rest/etsi/server/go/model_key_container_keys_inner.go

ekms/api/go/rest/etsi/server/go/model_key_ids_request.go

...est/etsi/server/go/model_key_ids_request_key_ids_inner.go

ekms/api/go/rest/etsi/server/go/model_key_request.go

ekms/api/go/rest/etsi/server/go/model_status.go

ekms/api/go/rest/etsi/server/go/routers.go

ekms/cmd/root.go

ekms/cmd/start.go

ekms/etsiqkdnclient/etsi-qkdn-client.go