What methods can be used to protect an API from unauthorized access and attacks?

The following methods are used to protect APIs from unauthorized access and attacks:

• Authentication and Authorization: Using tokens (JWT, OAuth), API keys, Basic Auth to verify user rights.
• Encryption: Transmitting data over HTTPS to prevent interception.
• Rate Limiting: Preventing DDoS attacks and abuse.
• Validation and Filtering of Incoming Data: Protecting against SQL injections, XSS, and other attacks.
• Logging and Monitoring: Tracking suspicious activity.
• Using CORS: Controlling access from different domains.
• Protection against CSRF: Using tokens or other mechanisms.

Example of simple authentication using an API key in Go:

func apiHandler(w http.ResponseWriter, r *http.Request) {
    apiKey := r.Header.Get("X-API-Key")
    if apiKey != "expected_api_key" {
        http.Error(w, "Unauthorized", http.StatusUnauthorized)
        return
    }
    // Handle the request
}