update flutter command code example

Example 1: update flutter

flutter upgrade

Example 2: flutter update

$ flutter channel

Example 3: update flutter version

I want to upgrade most latest version. So I used below commands:

flutter channel dev

Flutter has 4 project branches / channels ie stable, master, dev, beta. First 
when we install it. flutter install stable channel. If you want to switch :

flutter channel chanel_name

Then donwload that :

flutter upgrade