Lesson 8: Go setup and toolchain: Security and reliability

Concept Explanation

Reliable Go code handles failure paths as carefully as success paths. In this lesson, you will work with a small function that can fail, return clear errors, and protect the rest of the program from bad input. The focus is not on writing a lot of code, but on making the code honest: validate early, return useful errors, and keep the main flow easy to follow.

Where to Put the Code

1. Define color and position variables at the top.
2. Create shape drawing or placement logic in the middle.
3. Render output (print, canvas, SVG, or styled block) at the end.

Command Reference

• Validate input before doing the main work.
• Return clear errors that explain what failed without exposing unnecessary details.
• Keep success logic and error handling separate enough to scan quickly.
• Test both a normal input and a failure case before you move on.

Step-by-step Guide

1. Run the code with a valid input and confirm the expected result.
2. Change the input to an invalid value and observe the returned error.
3. Add one extra validation rule, such as a minimum length or forbidden value.
4. Refactor the function so the failure path is obvious at a glance.
5. Finish by checking that every path either returns a value or a useful error.

Practice Exercises

• Update the example so it accepts a username only when it contains letters and numbers.
• Write a second helper that validates an email-like string and returns a clear error on failure.
• Create a version that logs the error in main while keeping validation logic inside its own function.

Coding Challenges

• Handle several invalid input cases without turning the function into a long nested block.
• Design a small input-checking flow that is safe, readable, and easy to extend.

Mini Practice Tasks

• Add one more invalid test case and run it manually.
• Improve one error message so it is easier for a beginner to understand.
• Rename the validation function so its purpose is immediately obvious.