How to Build a REST API in Go using net/http
Building a REST API in Go is one of the most practical ways to learn how Go handles HTTP servers, JSON, and struct-based logic. In this tutorial, you’ll learn how to create a simple RESTful API using the standard net/http package—without using any third-party frameworks. This is a great starting point before moving to more complex architectures.
In this guide, we’ll create a simple API for managing books. Each book will have an ID, title, and author.
What You’ll Learn
- How to create HTTP server routes in Go
- How to handle GET, POST, PUT, and DELETE requests
- How to encode and decode JSON data
- How to organize handlers and write clean code
Step 1: Define a Book Struct
package main
type Book struct {
ID string `json:"id"`
Title string `json:"title"`
Author string `json:"author"`
}
We’ll use this struct to store data in memory.
Step 2: Step 2: Create a Global Book Slice
var books = []Book{
{ID: "1", Title: "Go Basics", Author: "John Doe"},
{ID: "2", Title: "Mastering Go", Author: "Jane Smith"},
}
Step 3: Create Handlers
Get All Books
func getBooks(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
json.NewEncoder(w).Encode(books)
}
Get a Single Book
func getBook(w http.ResponseWriter, r *http.Request) {
id := strings.TrimPrefix(r.URL.Path, "/books/")
for _, book := range books {
if book.ID == id {
json.NewEncoder(w).Encode(book)
return
}
}
http.NotFound(w, r)
}
Create a New Book
func createBook(w http.ResponseWriter, r *http.Request) {
var book Book
json.NewDecoder(r.Body).Decode(&book)
books = append(books, book)
w.WriteHeader(http.StatusCreated)
json.NewEncoder(w).Encode(book)
}
Update a Book
func updateBook(w http.ResponseWriter, r *http.Request) {
id := strings.TrimPrefix(r.URL.Path, "/books/")
for i, book := range books {
if book.ID == id {
json.NewDecoder(r.Body).Decode(&books[i])
w.WriteHeader(http.StatusOK)
json.NewEncoder(w).Encode(books[i])
return
}
}
http.NotFound(w, r)
}
Delete a Book
func deleteBook(w http.ResponseWriter, r *http.Request) {
id := strings.TrimPrefix(r.URL.Path, "/books/")
for i, book := range books {
if book.ID == id {
books = append(books[:i], books[i+1:]...)
w.WriteHeader(http.StatusNoContent)
return
}
}
http.NotFound(w, r)
}
Step 4: Set Up Routes
func main() {
http.HandleFunc("/books", getBooks)
http.HandleFunc("/books/", func(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case http.MethodGet:
getBook(w, r)
case http.MethodPost:
createBook(w, r)
case http.MethodPut:
updateBook(w, r)
case http.MethodDelete:
deleteBook(w, r)
default:
http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
}
})
fmt.Println("Server running on http://localhost:8080")
log.Fatal(http.ListenAndServe(":8080", nil))
}
Step 5: Run the Server
To run the server, save your code in a file named main.go and execute the following command in your terminal:
go run main.go
You should see the message Server running on http://localhost:8080.
You can now test your API using tools like Postman or curl.
Step 6: Test the API
Get All Books
curl -X GET http://localhost:8080/books
Get a Single Book
curl -X GET http://localhost:8080/books/1
Create a New Book
curl -X POST http://localhost:8080/books \
-H "Content-Type: application/json" \
-d '{"id":"3", "title":"Learning Go", "author":"Alice Johnson"}'
Update a Book
curl -X PUT http://localhost:8080/books/1 \
-H "Content-Type: application/json" \
-d '{"id":"1", "title":"Go Basics Updated", "author":"John Doe"}'
Delete a Book
curl -X DELETE http://localhost:8080/books/1
Conclusion
Congratulations! You’ve built a simple REST API in Go using the net/http package. This is just the beginning; you can extend this API by adding features like authentication, database integration, and more. Feel free to explore the Go documentation and other resources to deepen your understanding of Go and RESTful APIs.
If you have any questions or need further assistance, don’t hesitate to ask. Happy coding!