Is it necessary to add a return after logging an error in the handler when validation fails?

Yes, after logging an error in the HTTP handler upon failed validation, it is usually necessary to add a return. This prevents further execution of the code and sending an additional response to the client, which could lead to a panic or incorrect server behavior.

Example:

func handler(w http.ResponseWriter, r *http.Request) {
    if err := validate(r); err != nil {
        http.Error(w, err.Error(), http.StatusBadRequest)
        return // important to stop further execution
    }
    // rest of the request handling code
}