patterns

name	patterns
description	Project patterns including functional options, must pattern, caching decorator, error handling, configuration, and HTTP clients. Use when implementing common patterns in the codebase.
userInvokable	true

Project Patterns

References: Examples

Functional Options

Example

Use With* functions for configurable constructors:

func NewClient(baseURL string, options ...ClientOption) *Client {
    opts := defaultOptions()
    for _, option := range options {
        option(opts)
    }
    // create client...
}

client := NewClient(url, WithTimeout(30*time.Second), WithRetryCount(3))

Must Pattern

Example

Allowed only in cmd/, internal/apps/ - to fail fast on misconfiguration.

func Must[T any](f func() (T, error)) T {
    v, err := f()
    if err != nil { panic(err) }
    return v
}

Caching Decorator

Example

Wrap clients with cache layer for transparent caching.

Error Handling

Example

Rule	Example
Wrap with context	fmt.Errorf("get order %s: %w", id, err)
Check with Is/As	errors.Is(err, ErrNotFound)
Handle once	Don't log AND return
Custom errors	var ErrFoo = errors.New() or type FooError struct{}

Configuration

Example

Type	Path
App config	config/appconfig/{env}.json
Infra config	config/appconfig/infra-{env}.json
SSM	/myservice/{env}/app/config

Rules: No ARNs in app config, no secrets in files, use time.Duration with custom unmarshaler

HTTP Client with Retry

Example

client := tracing.NewRestyClient(baseURL,
    tracing.WithTimeout(30*time.Second),
    tracing.WithRetryCount(3),
    tracing.WithExponentialBackoff(true),
)

DynamoDB Key Design

Example

Use composite keys (PK + SK), GSIs for query patterns.

Feature Flags

Example

Fallback defaults, check at service layer, log evaluations.

JSON Tags

Example

Use camelCase for JSON tags and query params.

Request Validation

Example

Use ozzo-validation for struct validation.

Libraries

Library	Purpose
chi	HTTP router
samber/lo	Collections/utilities
ozzo-validation	Validation
resty	HTTP client