laravel validator make change error message for field code example

Example 1: how to add an custom error to validater error in laravel

if (request('event') == null) {
    $validator->errors()->add('event', 'Please select an event');
}

Example 2: laravel unique validation

unique:table,column,except,idColumn

############## Example : ################

############### For Updating  
//rules
'email' => 'unique:users,email_address,' . $userId,

############### For Creating 
//rules
'email' => 'unique:users,email_address',