Add the updateBook function to main.go:
func updateBook(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
params := mux.Vars(r)
for index, item := range books {
if item.ID == params["id"] {
books = append(books[:index], books[index+1:]...)
var book Book
_ = json.NewDecoder(r.Body).Decode(&book)
book.ID = params["id"]
books = append(books, book)
json.NewEncoder(w).Encode(book)
return
}
}
json.NewEncoder(w).Encode(books)
}