Go Config Yaml

In this tutorial, you'll learn about Go YAML Config: Unmarshal. We cover key concepts, practical examples, and best practices.

YAML configuration -- Parse YAML config files into Go structs using yaml:"key" struct tags.

The Problem

YAML parsing requires struct tags (yaml:"field_name") for field mapping. Missing tags or mismatched field names results in zero-value struct fields.

Wrong

type Config struct {
    DatabasePort int
    DatabaseHost string
}
yaml.Unmarshal(data, &cfg)

Output:

// Port=0, Host="" -- no yaml tags available

Right

type Config struct {
    Database struct {
        Port int    `yaml:"port"`
        Host string `yaml:"host"`
    } `yaml:"database"`
}
err := yaml.Unmarshal(data, &cfg)
if err != nil { log.Fatal(err) }

Output:

// Config populated correctly from YAML structure

Prevention

• Use yaml:"field_name" tags for all exported fields
• Match YAML hierarchy with nested Go structs
• Use inline:inline tag for flat maps
• Validate config after unmarshal with custom logic
• Use yaml.UnmarshalStrict to error on unknown fields

Common Mistakes with config yaml

1. Using head and tail instead of pattern matching, causing runtime errors on empty lists
2. Forgetting that lazy evaluation defers computation until the value is forced, causing space leaks with unevaluated thunks
3. Using return to exit a function early instead of wrapping a pure value in the monad

These mistakes appear frequently in real-world GO code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

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