Fetching and Parsing JSON

Fetching data from an HTTP endpoint in Go is straightforward and efficient, thanks to the net/http and encoding/json packages. Use http.Get for simple GET requests and parse JSON responses into structs with json.NewDecoder. For advanced use cases, http.Client provides control over headers, timeouts, and other HTTP methods. Always close response bodies with defer and validate status codes to ensure successful requests. With these tools, Go enables fast, reliable, and maintainable HTTP interactions.

This Go program fetches JSON data from a public API, validates the fetched data, and performs a validation.

package main
 
import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
)
 
type User struct {
	ID       int    `json:"id"`
	Name     string `json:"name"`
	Username string `json:"username"`
	Email    string `json:"email"`
}
 
func validateUser(user User) error {
	if user.Name == "" {
		return fmt.Errorf("validation error: user with ID %d has an empty name", user.ID)
	}
	if user.Email == "" {
		return fmt.Errorf("validation error: user with ID %d has an empty email", user.ID)
	}
	return nil
}
 
func main() {
	apiURL := "https://jsonplaceholder.typicode.com/users"
 
	resp, err := http.Get(apiURL)
	if err != nil {
		log.Fatalf("Failed to fetch data: %v", err)
	}
	defer resp.Body.Close()
 
	if resp.StatusCode != http.StatusOK {
		log.Fatalf("Unexpected status code: %d", resp.StatusCode)
	}
 
	var users []User
	if err := json.NewDecoder(resp.Body).Decode(&users); err != nil {
		log.Fatalf("Failed to parse JSON: %v", err)
	}
 
	allValid := true
	for _, user := range users {
		if err := validateUser(user); err != nil {
			log.Println(err)
			allValid = false
		}
	}
 
	if allValid {
		fmt.Println("✅ All user data passed validation")
		os.Exit(0) // success
	} else {
		fmt.Println("❌ Validation failed for some user data")
		os.Exit(1) // failure
	}
}

File Operations Web Service Without Dependencies