django.db.utils.OperationalError: could not translate host name "db" to address: Name or service not known

hey i am getting error when i install fabrick using the process mention in the redme for the installation of ubuntu 20.04 . the problem occured in django as mentioned : django.db.utils.OperationalError: could not translate host name "db" to address: Name or service not known
if you get the solution for that let everyone knows.