caching - Use memcached with laravel5 -

i'm configuring cache system on website, i'm having problem, when change:

'default' => env('cache_driver', 'file'),

to:

'default' => env('cache_driver', 'memcached'),

the framework using file method. know because returns error

class 'illuminate\cache\filestore' not have method 'tags'

but when call cache method this

cache::store('memcached')->tags('hello')->add('world', 'hello world', 10);

it works, if don't specify store shouldn't call default method assigned in cache config?

this line:

'default' => env('cache_driver', 'memcached'),

means use value of environment variable cache_driver. , default memcached if doesn't exist.

instead should change value in .env file:

cache_driver=memcached

UV code