json.Marshal返回奇怪的结果

Question

I'm trying to convert go structures to JSON. I thought I knew how to do it, but I'm confused by the output of this program. What am I missing?

package main
import "fmt"
import "encoding/json"

type Zoo struct {                                                                       
    name string
    animals []Animal
}
type Animal struct {
    species string
    says string
}

func main() {
    zoo := Zoo{"Magical Mystery Zoo",                                                   
         []Animal {
            { "Cow", "Moo"},
            { "Cat", "Meow"},
            { "Fox", "???"},
        },
    }
    zooJson, err := json.Marshal(zoo)
    if (err != nil) {
        fmt.Println(err)
    }

    fmt.Println(zoo)
    fmt.Println(zooJson)
}

Output:

{Magical Mystery Zoo [{Cow Moo} {Cat Meow} {Fox ???}]}
[123 125]

Expected Output (something along the lines of):

{Magical Mystery Zoo [{Cow Moo} {Cat Meow} {Fox ???}]}
{
    "name" : "Magical Mystery Zoo",
    "animals" : [{
             "name" : "Cow",
             "says" : "moo"
         }, {
             "name" : "Cat",
             "says" : "Meow"
         }, {
             "name" : "Fox",
             "says" : "???"
         }
    ]
 }

Where is [123 125] coming from?

Appreciate the help!

Answer 1

The result of marshaling is []byte so 123 and 125 is ascii for { and }

Struct fields have to be exported for marshaling to work:

Each exported struct field becomes a member of the object