Simple REST app using golang

simple_rest.go

package main

import (
	"encoding/json"
	"github.com/gorilla/mux"
	"log"
	"math/rand"
	"net/http"
	"strconv"
)

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

type Author struct {
	FirstName string `json:"first_name"`
	LastName string `json:"last_name"`
}

var books []Book

func getBooks(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(books)
}

func getBook(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	params := mux.Vars(r)
	for _, item := range books {
		if item.ID == params["id"] {
			json.NewEncoder(w).Encode(item)
			return
		}
	}
	json.NewEncoder(w).Encode(&Book{})
}

func createBook(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	var book Book
	_ = json.NewDecoder(r.Body).Decode(&book)
	book.ID = strconv.Itoa(rand.Intn(1000000))
	books = append(books, book)
	json.NewEncoder(w).Encode(book)
}

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)
		}
	}
	json.NewEncoder(w).Encode(books)
}

func deleteBook(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:]...)
			break
		}
	}
	json.NewEncoder(w).Encode(books)
}

func main() {
	r := mux.NewRouter()
	books = append(books, Book{ID: "1", Title: "Человек в высоком замке",
		Author: &Author{FirstName: "Филип", LastName: "Дик"}})
	r.HandleFunc("/books", getBooks).Methods("GET")
	r.HandleFunc("/books/{id}", getBook).Methods("GET")
	r.HandleFunc("/books", createBook).Methods("POST")
	r.HandleFunc("/books/{id}", updateBook).Methods("PUT")
	r.HandleFunc("/books/{id}", deleteBook).Methods("DELETE")
	log.Fatal(http.ListenAndServe(":8000", r))
}