appcontext

appcontext — request-scoped context value helpers

import "github.com/downsized-devs/sdk-go/appcontext"

Stability: Stable — see STABILITY.md

Typed get/set helpers for the values logger, audit, and others expect to find on context.Context — request ID, user ID, accept-language, service version, device type, app response code.

Features

• Setter/getter pairs with private context keys (no collisions with other packages)
• Read by logger for automatic field enrichment
• Zero external dependencies

Installation

go get github.com/downsized-devs/sdk-go/appcontext

Quick Start

package main

import (
    "context"

    "github.com/downsized-devs/sdk-go/appcontext"
)

func main() {
    ctx := context.Background()
    ctx = appcontext.SetRequestId(ctx, "req-abc")
    ctx = appcontext.SetUserId(ctx, 42)

    _ = appcontext.GetRequestId(ctx) // "req-abc"
    _ = appcontext.GetUserId(ctx)    // 42
}

API Reference

All Set* return a new context.Context; the original is not mutated.

Examples

Gin middleware that populates everything from headers

func ContextEnricher() gin.HandlerFunc {
    return func(c *gin.Context) {
        ctx := c.Request.Context()
        ctx = appcontext.SetRequestId(ctx, c.GetHeader(header.RequestID))
        ctx = appcontext.SetAcceptLanguage(ctx, c.GetHeader(header.AcceptLanguage))
        ctx = appcontext.SetServiceVersion(ctx, buildSHA)
        c.Request = c.Request.WithContext(ctx)
        c.Next()
    }
}

Error Handling

Getters return the zero value when the key is unset; no error is returned. Callers that require a value should validate at their own boundary.

Dependencies

• Internal: codes, header, language
• External: stdlib only

Testing

go test ./appcontext/...

Contributing

See CONTRIBUTING.md. Adding a new key is additive — pair every Set* with a Get* and update logger if the field should appear in log lines automatically.

Related Packages

• logger — primary consumer.
• header — string constants for HTTP header names.
• translator — reads AcceptLanguage.
• audit — reads RequestId and UserId.