package data

...

func (m MovieModel) Delete(id int64) error {
    // Return an ErrRecordNotFound error if the movie ID is less than 1.
    if id < 1 {
        return ErrRecordNotFound
    }

    // Construct the SQL query to delete the record.
    query := `
        DELETE FROM movies
        WHERE id = $1`

    // Execute the SQL query using the Exec() method, passing in the id variable as
    // the value for the placeholder parameter. The Exec() method returns a sql.Result
    // value.
    result, err := m.DB.Exec(query, id)
    if err != nil {
        return err
    }

    // Call the RowsAffected() method on the sql.Result value to get the number of rows
    // affected by the query.
    rowsAffected, err := result.RowsAffected()
    if err != nil {
        return err
    }

    // If no rows were affected, we know that the movies table didn't contain a record
    // with the provided ID at the moment we tried to delete it. In that case we 
    // return an ErrRecordNotFound error.
    if rowsAffected == 0 {
        return ErrRecordNotFound
    }

    return nil
}

package main

...

func (app *application) deleteMovieHandler(w http.ResponseWriter, r *http.Request) {
    // Extract the movie ID from the URL.
    id, err := app.readIDParam(r)
    if err != nil {
        app.notFoundResponse(w, r)
        return
    }

    // Delete the movie from the database, sending a 404 Not Found response to the
    // client if there isn't a matching record.
    err = app.models.Movies.Delete(id)
    if err != nil {
        switch {
        case errors.Is(err, data.ErrRecordNotFound):
            app.notFoundResponse(w, r)
        default:
            app.serverErrorResponse(w, r, err)
        }
        return
    }

    // Return a 200 OK status code along with a success message.
    err = app.writeJSON(w, http.StatusOK, envelope{"message": "movie successfully deleted"}, nil)
    if err != nil {
        app.serverErrorResponse(w, r, err)
    }
}

package main

...

func (app *application) routes() http.Handler {
    router := httprouter.New()

    router.NotFound = http.HandlerFunc(app.notFoundResponse)
    router.MethodNotAllowed = http.HandlerFunc(app.methodNotAllowedResponse)

    router.HandlerFunc(http.MethodGet, "/v1/healthcheck", app.healthcheckHandler)
    router.HandlerFunc(http.MethodPost, "/v1/movies", app.createMovieHandler)
    router.HandlerFunc(http.MethodGet, "/v1/movies/:id", app.showMovieHandler)
    router.HandlerFunc(http.MethodPut, "/v1/movies/:id", app.updateMovieHandler)
    // Add the route for the DELETE /v1/movies/:id endpoint.
    router.HandlerFunc(http.MethodDelete, "/v1/movies/:id", app.deleteMovieHandler)

    return app.recoverPanic(router)
}