Building a Calculator in Go: A Masterclass in Software Engineering Best Practices

When I set out to build a calculator in Go, I thought it would be a weekend project. After all, how complex could a calculator be? I could not have been more wrong. What started as a simple calculator evolved into a complete software engineering bootcamp. From requirements to architecture, from testing to security, this tiny project taught me more about professional development than many large-scale systems I have worked on. The Humble Calculator: More Complex Than You Think Before writing code, I asked myself: what does a professional calculator actually need? Basic arithmetic and advanced functions A responsive graphical interface A command-line interface for power users Calculation history Cross-platform compatibility Comprehensive tests A secure API layer serving both interfaces This became my requirements document, forcing me to think about edge cases and constraints before coding. Lesson 1: Even small projects benefit from written requirements. Architecture: Layering Like an Onio