Go Http

GO HTTP handy cheats

Unmarshal JSON into a struct

Mapping json data directly into a defined struct

  </div>

type Book struct {
  Title string `json:"title"`
  Author string `json:"author"`
}

const bookUrl = "https://api.examplebooks.com/q=\"Pat+Rothfuss\""

func getBooks() ([]Book, error) {
    res, err := http.Get(url)
    if err != nil {
	return nil, fmt.Errorf("error creating request: %w", err)
    }
    defer res.Body.Close()

    data, err := io.ReadAll(res.Body)
    if err != nil  {
    	return nil, fmt.Errorf("error reading response body: %w", err)
    }

    books := []Book{}

    if err = json.Unmarshal(data, &books); err != nil {
	return nil, err
    }	

    return books, nil
}

Unmarshal JSON into a map

If the structure of the response resource is unknown or doesn't map to a defined struct, a map[string]any can be used as a catch all.

  </div>

const bookUrl = "https://api.examplebooks.com/q=\"Pat+Rothfuss\""

func getBooks() ([]map[string]any, error) {
    // any is an alias for interface{}
    // var book []map[string]interface{} is the same
    var books []map[string]any

    res, err := http.Get(url)
    if err != nil {
	return books, fmt.Errorf("error creating request: %w", err)
    }
    defer res.Body.Close()

    data, err := io.ReadAll(res.Body)
    if err != nil  {
    	return books, fmt.Errorf("error reading response body: %w", err)
    }
 
    if err = json.Unmarshal(data, &books); err != nil {
	return books, err
    }	

    return books, nil
}

Use a json decoder

Decoders accept a io.Reader, allowing data to be streamed which is better for large data sets. The Response body is an io.Reader already.

  </div>

type Book struct {
  Title string `json:"title"`
  Author string `json:"author"`
}
const bookUrl = "https://api.examplebooks.com/q=\"Pat+Rothfuss\""

func getBook() (Book, error) {
    res, err := http.Get(url)
    if err != nil {
	return Book{}, fmt.Errorf("error creating request: %w", err)
    }
    defer res.Body.Close()

    var book Book
    decoder := json.NewDecoder(res.Body)
    err = decoder.Decode(&book)
    if err != nil {
	return Book{}, nil
    }

    return book, nil
}