go - Convert interface{} to int

Question

I'm trying to get a value from a JSON and cast it to int but it doesn't work, and I don't know how to do it properly.

Here is the error message:

...cannot convert val (type interface {}) to type int: need type assertion

And the code:

    var f interface{}
    err = json.Unmarshal([]byte(jsonStr), &f)
    if err != nil {
        utility.CreateErrorResponse(w, "Error: failed to parse JSON data.")
        return
    }

    m := f.(map[string]interface{})

    val, ok := m["area_id"]
    if !ok {
        utility.CreateErrorResponse(w, "Error: Area ID is missing from submitted data.")
        return
    }

    fmt.Fprintf(w, "Type = %v", val)   // <--- Type = float64
    iAreaId := int(val)                // <--- Error on this line.
    testName := "Area_" + iAreaId      // not reaching here

Answer 1

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