git clone 'Authentication failed' error

git clone error log : 

Cloning into 'my_project'...
fatal: Authentication failed for 'www.github.com/my_newtoy_project/project.git'

 

 

 

Resolution(root permissin required): 

 

$ git config --system -unset credential.helper

 

or 

 

global cmd

$ git config --global -unset credential.helper