What is usually contained in the request body in REST?

In REST, the request body usually contains data that the client sends to the server to create or update a resource. The format is most often JSON or XML, but JSON is the most common.

Typical content of the request body:

• Representation of the resource with the necessary fields (e.g., a JSON object with parameters).
• For POST requests — data of the new resource.
• For PUT/PATCH — updated fields of the resource.

Example of a JSON request body for creating a user:

{
  "name": "Ivan Ivanov",
  "email": "ivan@example.com",
  "age": 30
}

In Go, when working with REST API, the request body is usually read and deserialized into a structure:

Type User struct {
    Name  string `json:"name"`
    Email string `json:"email"`
    Age   int    `json:"age"`
}

func handler(w http.ResponseWriter, r *http.Request) {
    var user User
    err := json.NewDecoder(r.Body).Decode(&user)
    if err != nil {
        http.Error(w, "Invalid request body", http.StatusBadRequest)
        return
    }
    // process user
}

Thus, the request body in REST contains the data necessary to perform an operation on the resource.