How to build a RESTful API and handle errors using Golang?

This article shows the steps to build a RESTful API using Golang, including importing the necessary packages, creating a router, defining handlers, registering routes, and starting the server. In addition, instructions are provided for handling error conditions, such as returning error messages and correct HTTP status codes.

Use Golang to build a RESTful API and handle errors

Building a RESTful API in Golang is simple and efficient. This article will take you step by step to understand how to create an API and Handle common error scenarios.

1. Import necessary packages

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"

    "github.com/gorilla/mux"
)

2. Create router

r := mux.NewRouter()

3. Define handler

func indexHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "Hello, World!")
}

func postHandler(w http.ResponseWriter, r *http.Request) {
    var data map[string]interface{}
    if err := json.NewDecoder(r.Body).Decode(&data); err != nil {
        http.Error(w, "Invalid JSON", http.StatusBadRequest)
        return
    }

    log.Printf("Received data: %v", data)
    json.NewEncoder(w).Encode(map[string]interface{}{"status": "success"})
}

4. Register route

r.HandleFunc("/", indexHandler).Methods("GET")
r.HandleFunc("/post", postHandler).Methods("POST")

5. Start the server

http.ListenAndServe(":8080", r)

Practical case

Create a simple API to store and retrieve user data:

type User struct {
    Name  string `json:"name"`
    Email string `json:"email"`
}

func userHandler(w http.ResponseWriter, r *http.Request) {
    switch r.Method {
    case "GET":
        json.NewEncoder(w).Encode([]User{{Name: "John", Email: "john@example.com"}})
    case "POST":
        var user User
        if err := json.NewDecoder(r.Body).Decode(&user); err != nil {
            http.Error(w, "Invalid JSON", http.StatusBadRequest)
            return
        }
        fmt.Fprint(w, "User created:", user)
    default:
        http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
    }
}

Then register the route:

r.HandleFunc("/users", userHandler)

Now you can easily test the API using curl or other tools:

curl -X GET localhost:8080/users

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