Skill

go-error-wrapping

Wrap errors with context using fmt.Errorf %w pattern

npx claudepluginhub jamesprial/prial-plugins --plugin golang-workflow

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Use `fmt.Errorf` with `%w` to add context while preserving the error chain.

SKILL.md

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Last CommitJan 19, 2026

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Error Wrapping with %w

Pattern

Use fmt.Errorf with %w to add context while preserving the error chain.

CORRECT

func ReadConfig(path string) (*Config, error) { data, err := os.ReadFile(path) if err != nil { return nil, fmt.Errorf("read config %s: %w", path, err) } var cfg Config if err := json.Unmarshal(data, &cfg); err != nil { return nil, fmt.Errorf("parse config %s: %w", path, err) } return &cfg, nil }

WRONG

// Bad: Loses error chain return nil, fmt.Errorf("read config failed: %v", err) // Bad: No context return nil, err // Bad: String concatenation return nil, errors.New("read config: " + err.Error())

Key Rules

Use %w to wrap, not %v or %s

Add meaningful context (file names, IDs, operations)

Keep messages lowercase, no punctuation

Preserve original error for type checking

Example Chain

// Error flows up with context at each layer: // "process user 123: read config /etc/app.conf: open /etc/app.conf: no such file or directory" func ProcessUser(id int) error { cfg, err := ReadConfig("/etc/app.conf") if err != nil { return fmt.Errorf("process user %d: %w", id, err) } // use cfg... return nil }

Error Wrapping with %w

Pattern

Use fmt.Errorf with %w to add context while preserving the error chain.

CORRECT

func ReadConfig(path string) (*Config, error) {
    data, err := os.ReadFile(path)
    if err != nil {
        return nil, fmt.Errorf("read config %s: %w", path, err)
    }

    var cfg Config
    if err := json.Unmarshal(data, &cfg); err != nil {
        return nil, fmt.Errorf("parse config %s: %w", path, err)
    }

    return &cfg, nil
}

WRONG

// Bad: Loses error chain
return nil, fmt.Errorf("read config failed: %v", err)

// Bad: No context
return nil, err

// Bad: String concatenation
return nil, errors.New("read config: " + err.Error())

Key Rules

Use %w to wrap, not %v or %s
Add meaningful context (file names, IDs, operations)
Keep messages lowercase, no punctuation
Preserve original error for type checking

Example Chain

// Error flows up with context at each layer:
// "process user 123: read config /etc/app.conf: open /etc/app.conf: no such file or directory"

func ProcessUser(id int) error {
    cfg, err := ReadConfig("/etc/app.conf")
    if err != nil {
        return fmt.Errorf("process user %d: %w", id, err)
    }
    // use cfg...
    return nil
}