* feat(goctl): supports api multi-level importing
Resolves: #1744
* fix(goctl): import-cycle, etc.
import-cycle will not be allowed
e.g., a.api -> b.api -> a.api
regular multiple-import will be allowed
e.g., a.api -> b.api -> c.api
-> c.api
* refactor(goctl): adds comments to exported var
* fix(goctl): typo in a comment