json serialize nil slice

main.go

// https://forum.golangbridge.org/t/slice-pass-as-value-or-pointer/2866/2

package main
import (
    "fmt"
    "reflect"
    "encoding/json"
)
type TTT struct {
    arr []int
}
func main() {
    fmt.Println("Hello, playground")
    
    var a []int
    b := []int{}
    
    fmt.Printf("%T %v %v %v\n%T %v %v %v\n", a, a, reflect.TypeOf(a).String(), &a, b, b, reflect.TypeOf(b).String(), &b)
    
    sA := TTT{arr: a}
    sB := TTT{arr: b}
    
    fmt.Println(sA, sB)
    
    byteA, _ := json.Marshal(a)
    byteB, _ := json.Marshal(b)
    
    fmt.Println(string(byteA), string(byteB))
    
    byteSA, _ := json.Marshal(sA)
    byteSB, _ := json.Marshal(sB)
    
    fmt.Println(string(byteSA), string(byteSB))
}