Course outline

01 · Getting Started

02 · Variables, Types & Control Flow

03 · Functions & Composite Types

04 · Methods, Interfaces & Errors

05 · Packages, Modules & Concurrency Intro

06 · Your First Real Program

07 · Testing & Debugging in Go

08 · Capstone — Ship a Real Tool

Stage 1 · Code

Capstone — Ship a Real Tool

Flags & Environment Config

Load configuration from flags, environment variables, and defaults — with clear validation and startup error messages.

7 min readProgramming Foundations (Go)Code

Config Struct

Collect all configuration into a single struct. This makes configuration explicit, testable, and easy to pass through the application without global variables.

Goconfig-struct.go

35 linesLn 1, Col 1Go

Environment Variables

os.LookupEnv returns the value and a boolean indicating whether the variable was set. This lets you distinguish 'not set' from 'set to empty string'.

Goloading-from-environment.go

32 linesLn 1, Col 1Go

Flags Override Env

The standard precedence is: defaults → environment variables → flags. Flags win because they are explicit. Apply env first, then parse flags, then let flags override env.

Goload-order:-defaults-→-env-→-flags.go

47 linesLn 1, Col 1Go

Validation and Startup Errors

Validate configuration before starting the server. Fast-fail at startup with clear messages — a missing config found at startup is far cheaper than one found under load.

Goconfig-validation.go

27 linesLn 1, Col 1Go

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