JSON Marshalling & Unmarshalling

JSON in Go

This lesson explains the main concept clearly with beginner-friendly examples and background so you can learn why the code works.

The encoding/json package provides Marshal and Unmarshal.

type User struct {
    ID   int    `json:"id"`
    Name string `json:"name"`
    Age  int    `json:"age,omitempty"`
}

u := User{ID: 1, Name: "Alice"}
bytes, _ := json.Marshal(u)
fmt.Println(string(bytes)) // {"id":1,"name":"Alice"}

Decoding from a request body

func createUser(w http.ResponseWriter, r *http.Request) {
    var u User
    if err := json.NewDecoder(r.Body).Decode(&u); err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return
    }
    // process u …
    w.WriteHeader(http.StatusCreated)
}

Custom Marshal/Unmarshal

Implement the json.Marshaler and json.Unmarshaler interfaces for special handling.