Sudo apt-get not working in 18.04 [duplicate]

Solution 1:

Unfortunately, the problem was in my college network, i used my phone hotspot and it worked. "AWESOME"

Solution 2:

It looks like Upgrade from 16.04 to 18.04 has messed up your source list. Replace existing contents in /etc/apt/sources.list file with following lines. Backup and Remove existing other source lists in /etc/apt/sources.list.d/ to avoid any conflict.

#------------------------------------------------------------------------------#
#                            OFFICIAL UBUNTU REPOS                             #
#------------------------------------------------------------------------------#


###### Ubuntu Main Repos
deb http://in.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse 

###### Ubuntu Update Repos
deb http://in.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse 
deb http://in.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse

Run sudo apt update after it. Issue should be resolved.