* [go-experimental] export required fields without pointer, only omitempty if type is not required and not nullable
* fix: go-experimental sample code
* fix: export nullable field as pointer
* update samples
* feat: nullable types
* add getter/setter for required fields, improve docstring
* [Go][experimental-client] Properly define packageName for go-experimental sample client
* [Go][experimental-client] make structure members pointers, provide custom marshalling.