如果Golang中有相同的对象，则初始化嵌套的struct定义

I have struct like this:

type AutoGenerated struct {
 Accounting []struct {
    FirstName string `json:"firstName"`
    LastName string `json:"lastName"`
    Age int `json:"age"`
} `json:"accounting"`
Sales []struct {
    FirstName string `json:"firstName"`
    LastName string `json:"lastName"`
    Age int `json:"age"`
} `json:"sales"`

I want to assign values to it like this:-

data := AutoGenerated{}
data.Accounting.LastName = "Apple2"
data.Accounting.FirstName = "Apple1"
data.Accounting.Age = 20
data.Sales.LastName = "Ball2"
data.Sales.FirstName = "Ball1"
data.Sales.Age = 30

But is is giving error which is data.Accounting.LastName undefined

Although same code is working fine for

type AutoGenerated struct {
    FirstName string `json:"firstName"`
    LastName string `json:"lastName"`
    Age int `json:"age"`
}

Where I assigned the values like this:-

data := AutoGenerated{}
data.LastName = "Apple2"
data.FirstName = "Apple1"
data.Age = 20

Please don't assign values manually I have to take values from other function.