POST call failing with JSON

Question

I have an API which accepts a request body like this:

The content-type is application/json.

{
  "firstname": "foo",
  "surname": "bar",
  "age": 10,
  "group":"test"
}

The request goes through when I use a client like Postman.

However, the same request fails from Go:

    type Student struct {
        firstname string
        surname   string
        age       int
        group     string
    }
    student:= Student{"foo", "bar", 10, "test"}
    b, err := json.Marshal(student)

    rest := restCall("POST", "http://api", b, "xyz123")

    func restCall(method string, url string, body []byte, token string)  {

        req, _ := http.NewRequest(method, url, bytes.NewReader(body))

        req.Header.Add("Authorization", token)
        req.Header.Add("content-type", "application/json")

        res, _ := http.DefaultClient.Do(req)

        defer res.Body.Close()
    }

I get an internal HTTP 500 error stating :

Mandatory parameter 'group' is missing.

But, I did pass it as you can see from my code.

This is an obvious duplicate. We get about 3 of these per week. There's no reason to leave them all open. — Jonathan Hall, Jan 05 '19 at 15:26
It's also worth noting that having multiple duplicates does _not_ make the question harder to discover. This question still exists... and now points to the duplicate, so your concern that newcomers would benefit by finding this question is _not_ a reason not to mark as duplicate. — Jonathan Hall, Jan 05 '19 at 15:36

score 1 · Accepted Answer · answered Jan 05 '19 at 15:27

Your code has several issues: 1. Structure must have public fields and fields should be tagged. Then it will be serialized properly:

type Student struct {
    Firstname string `json:"firstname"`
    Surname   string `json: "surname"`
    Age       int .  `json: "age"`
    Group     string `json: "group"`
}

2. Never ignore errors returned by method call. So you will not miss issues in your code:

b, err := json.Marshal(student)
if err != nil {
    fmt.Println(err)
}

And the same after calls of NewRequest and DefaultClient.Do

POST call failing with JSON

1 Answers1