When push in github, why git didn't ask me to type username and password?
You can manually unset credential.helper by running below command.
git config --global --unset credential.helper
use --global
or --local
or --system
as per your needs.
Then pushing in github will ask for username and password.
If you are on windows one other way to do this is as below but note that it will again save your credentials if you use credential.helper with git.
Go to control panel
-> Credential Manager
-> Windows Credentials
and remove your git credential entry/entries.
This might help.. https://help.github.com/articles/caching-your-github-password-in-git/
Git by default saves your passwd in cache for 15 min.
For Mac users password can be clear by running below command :
git credential-osxkeychain erase
host=github.com
protocol=https