Sudo requires password after adding user to sudoers

Solution 1:

You should use NOPASSWD option

aman ALL=(ALL) NOPASSWD:ALL

However, I would not recommend it that way, because user aman can execute anything without password. I would only allow the systemctl command to be executed without password like this:

aman     ALL=NOPASSWD:/bin/systemctl

It is safer that way.

Solution 2:

This is the normal behaviour, being in the sudoers list only means that you can use the sudo command, but you'll be asked for your password.

If you want to use sudo without password, you need to add NOPASSWD:ALL after aman ALL=(ALL:ALL) in /etc/sudoers

(the line would look like aman ALL=(ALL:ALL) NOPASSWD:ALL)

see here