In this tutorial, we'll be exploring how to build RESTful APIs with Go programming. We'll start by defining what a RESTful API is, then move on to setting up our Go environment and building a simple API. By the end of this tutorial, you'll have a solid understanding of how to build RESTful APIs with Go and be able to use this knowledge to create your own APIs.


What is a RESTful API?

REST stands for Representational State Transfer. RESTful APIs are web services that adhere to the REST architecture and use HTTP methods to interact with resources. A resource is any object that can be accessed through a URI (Uniform Resource Identifier). RESTful APIs use HTTP methods to perform CRUD (Create, Read, Update, Delete) operations on these resources.


Setting Up Your Environment

Before we can start building our API, we need to set up our Go environment. You'll need to have Go installed on your machine. If you haven't already, you can download it from the official website at https://golang.org/dl/. Once you have Go installed, you can create a new project folder for your API.


Creating a Simple RESTful API

Now that we have our environment set up, we can start building our API. In this tutorial, we'll be building a simple API that allows users to create and retrieve books. We'll be using the Gorilla mux router to handle our HTTP requests.

First, we need to import the necessary packages:

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"
    "github.com/gorilla/mux"
)


Next, we'll define our book struct:

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

Now, we'll create a slice of books to store our books:

var books []Book

Let's create some dummy data to work with:

books = append(books, Book{ID: "1", Title: "The Catcher in the Rye", Author: "J.D. Salinger", Year: 1951})
books = append(books, Book{ID: "2", Title: "To Kill a Mockingbird", Author: "Harper Lee", Year: 1960})

We'll create our endpoints using the Gorilla mux router. Let's start with our GET endpoint to retrieve all books:

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

Next, let's create an endpoint to retrieve a single book:

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

Now, we'll create an endpoint to create a new 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 = fmt.Sprintf("%d", len(books)+1
books = append(books, book)
json.NewEncoder(w).Encode(book)
}

Finally, we'll create an endpoint to delete a book: 

func deleteBook(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    params := mux.Vars(r)
    for index, book := range books {
        if book.ID == params["id"] {
            books = append(books[:index], books[index+1:]...)
            break
        }
    }
    json.NewEncoder(w).Encode(books)
}

Now, let's create our main function to start our server:

func main() {
    router := mux.NewRouter()

    router.HandleFunc("/api/books", getBooks).Methods("GET")
    router.HandleFunc("/api/books/{id}", getBook).Methods("GET")
    router.HandleFunc("/api/books", createBook).Methods("POST")
    router.HandleFunc("/api/books/{id}", deleteBook).Methods("DELETE")

    log.Fatal(http.ListenAndServe(":8000", router))
}

That's it! You can now start your server by running the main function. Navigate to http://localhost:8000/api/books to retrieve all books. To retrieve a single book, use http://localhost:8000/api/books/{id}, where {id} is the ID of the book you want to retrieve. To create a new book, send a POST request to http://localhost:8000/api/books with the book data in JSON format. To delete a book, send a DELETE request to http://localhost:8000/api/books/{id}, where {id} is the ID of the book you want to delete.


Conclusion

In this tutorial, we've covered the basics of building RESTful APIs with Go programming. We've used the Gorilla mux router to handle our HTTP requests and created endpoints for retrieving all books, retrieving a single book, creating a new book, and deleting a book. This is just the beginning of what you can do with Go and RESTful APIs. With this knowledge, you can now start building your own APIs and integrating them into your applications.