@Arunraj this may be due to package mismatch, make sure you are using node version 14.9.0, typescript version 3.7.2
try to reinstall packages with below comments
npm install typedi@0.8.0 --save
npm install typeorm@0.2.5 --save
npm install typeorm-typedi-extensions@0.2.1 --save
and then give npm start serve