brew

PROBLEM
I ran 

brew upgrade

It updated my mysql installation to  8.0.12. Previously I was working with 5.7.22. Now each time I start mysql using the following commands

mysql.server start

OR

brew services mysql restsrt 

MySQL does not start properly

 Most probably the error you will face is 

.. ERROR! The server quit without updating PID file

SOLUTION 

When I run