feat(extgen): support for mixed type (#1913)
* feat(extgent): support for mixed type
* refactor: use unsafe.Pointer
* Revert "refactor: use unsafe.Pointer"
This reverts commit 8a0b9c1beb3312627819d5003f67b14088442925.
* fix docs
* fix docs
* cleanup template
* fix template
* fix tests
