is it reasonable for goword.GetSpace returing *space object instead of Ispace?

[MistarQ]

here is the seene

type MySpace struct { goworld.Space // Space type should always inherit from entity.Space }

i create a space called mySpace, if i use
func GetSpace(id common.EntityID) *Space
i will get an *Space and i can not change it into mySpace unless use
mySpace := (*MySpace)(unsafe.Pointer(space))

and if i change GetSpace into
func GetSpace(id EntityID) entity.ISpace { return entity.GetSpaceI(id) }

then we can easily cast ISpace into mySpace

ms := goworld.GetSpaceI(monster.Space.ID).(*MySpace)``

[MistarQ]

其实就是想问多态的情况下是否应该返回接口Ispace而非父类对象*Space