In commandline type:
$ sudo visudo
It opens a file /etc/sudoers in nano text editor, as /etc/sudoers.tmp
Add the last line:
yourusername ALL=(ALL) NOPASSWD: ALL
# This file MUST be edited with the 'visudo' command as root.
# Please consider adding local content in /etc/sudoers.d/ instead of
# directly modifying this file.
# See the man page for details on how to write a sudoers file.
# Host alias specification
# User alias specification
# Cmnd alias specification
# User privilege specification
root ALL=(ALL:ALL) ALL
# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL
# Allow members of group sudo to execute any command
%sudo ALL=(ALL:ALL) ALL
# See sudoers(5) for more information on "#include" directives:
mike ALL=(ALL) NOPASSWD: ALL
My username is mike, so I added mike ALL=(ALL) NOPASSWD: ALL as you can see above.
Press Ctrl + X to exit nano and confirm writhing changes to the file with "y".
Now it's done, it should work without restarting or reloading anything.