go - golang json marshal: how to omit empty nested struct

Question

go playground

As shown in the code above, one can use json:",omitempty" to omit certain fields in a struct to appear in json.

For example

type ColorGroup struct {
    ID     int `json:",omitempty"`
    Name   string
    Colors []string
}
type Total struct {
    A ColorGroup`json:",omitempty"`
    B string`json:",omitempty"`
}
group := Total{
       A: ColorGroup{},

}

In this case, B won't show up in json.Marshal(group)

However, if

group := Total{
       B:"abc",

}

A still shows up in json.Marshal(group)

{"A":{"Name":"","Colors":null},"B":"abc"}

Question is how do we get only

{"B":"abc"}

EDIT: After some googling, here is a suggestion use pointer, in other words, turn Total into

type Total struct {
    A *ColorGroup`json:",omitempty"`
    B string`json:",omitempty"`
}

Answer 1

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