BUG - Express 4 is an invalid dependency

Problem

• Clone repository
• Run npm install
• Run npm start
• See error: typeerror app.configure is not a function

Environment

• OS | Ubuntu 20.04.2 LTS
• Git | 2.25.1
• Node | 10.18.0
• NPM | 6.13.4

Solution

• Downgrade package.json express from 4.17.1 to 3.21.2

References

• Stackoverflow Comment
• ExpressJS Documentation