Go: json.Marshal(struct) returns {}

Question

type TestObject struct {
    kind string `json:"kind"`
    id   string `json:"id, omitempty"`
    name  string `json:"name"`
    email string `json:"email"`
}

func TestCreateSingleItemResponse(t *testing.T) {
    testObject := new(TestObject)
    testObject.kind = "TestObject"
    testObject.id = "f73h5jf8"
    testObject.name = "Yuri Gagarin"
    testObject.email = "Yuri.Gagarin@Vostok.com"

    fmt.Println(testObject)

    b, err := json.Marshal(testObject)

    if err != nil {
        fmt.Println(err)
    }

    fmt.Println(string(b[:]))
}

Here is the output:
[ `go test -test.run="^TestCreateSingleItemResponse$"` | done: 2.195666095s ]
    {TestObject f73h5jf8 Yuri Gagarin Yuri.Gagarin@Vostok.com}
    {}
    PASS

Why is the JSON essentially empty?

Chris Gregori · Accepted Answer

You need to export the fields in TestObject by capitalizing the first letter in the field name. Change kind to Kind and so on. type TestObject struct { Kind string `json:"kind"` Id string `json:"id,omitempty"` Name string `json:"name"` Email string `json:"email"` } The encoding/json package and similar packages ignore unexported fields. package main import ( "encoding/json" "fmt" ) type TestObject struct { Kind string `json:"kind"` ID string `json:"id omitempty"` Name string `json:"name"` Email string `json:"email"` } func main() { testObject := new(TestObject) testObject.Kind = "TestObject" testObject.ID = "f73h5jf8" testObject.Name = "Yuri Gagarin" testObject.Email = "Yuri.Gagarin@Vostok.com" fmt.Println(testObject) b, err := json.Marshal(testObject) if err != nil { fmt.Println(err) } fmt.Println(string(b[:])) } https://play.golang.org/p/hs01TqqApeH The `json:"..."` strings that follow the field declarations are struct tags. The tags in this struct set the names of the struct's fields when marshaling to and from JSON.

Go Language

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