golib/context

Context Package

Thread-safe context management with generic key-value storage, extending Go's standard context.Context.

AI Disclaimer (EU AI Act Article 50.4): AI assistance was used solely for testing, documentation, and bug resolution under human supervision.

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Table of Contents

• Overview
• Key Features
• Architecture
• Installation
• Quick Start
• Core Concepts
• Operations
• Performance
• Use Cases
• Advanced Usage
• Gin Integration
• Best Practices
• Testing
• Contributing
• Future Enhancements
• Related Documentation
• License

---

Overview

The context package provides a thread-safe, generic context management system that extends Go's standard context.Context with advanced key-value storage capabilities. It enables you to store, retrieve, and manage configuration data within contexts while maintaining full compatibility with the standard library.

Design Philosophy

1. Generic & Type-Safe: Use any comparable type as keys (string, int, custom types)
2. Thread-Safe: All operations are concurrent-safe using sync.Map and sync.RWMutex
3. Context Compatible: Implements context.Context interface fully
4. Zero Dependencies: Core package has no external dependencies
5. Extensible: Framework integration packages (e.g., Gin) built on top

Why Use This Package?

• ✅ Type-safe key-value storage within contexts
• ✅ Thread-safe operations for concurrent access
• ✅ Context cloning with independent storage
• ✅ Configuration merging from multiple sources
• ✅ Atomic operations (LoadOrStore, LoadAndDelete)
• ✅ Flexible iteration with Walk and WalkLimit
• ✅ Full context.Context compatibility
• ✅ Framework integrations (Gin, and more)

---

Key Features

Feature	Description	Benefit
Generic Keys	Use any comparable type as keys	Type safety and flexibility
Thread-Safe	Concurrent-safe storage and retrieval	Safe for goroutines
Context Cloning	Create independent copies	Isolated configuration spaces
Configuration Merging	Combine multiple configs	Flexible configuration composition
Walk Operations	Iterate over stored values	Inspection and transformation
Atomic Operations	LoadOrStore, LoadAndDelete	Race-free updates
Cancellation	Proper context cancellation handling	Resource cleanup
Gin Integration	Seamless Gin framework support	Web application context

---

Architecture

Package Structure

context/
├── interface.go      # Core interfaces and factory functions
├── model.go          # Config implementation
├── map.go            # MapManage implementation helpers
├── helper.go         # Utility functions
├── context.go        # Context management
└── gin/              # Gin framework integration
    ├── interface.go  # Gin-specific context wrapper
    └── model.go      # Implementation

Component Architecture

┌─────────────────────────────────────────────────────────┐
│              Config[T comparable]                        │
│                                                          │
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐ │
│  │   context.   │  │  MapManage   │  │   Context    │ │
│  │   Context    │  │  [T]         │  │              │ │
│  └──────────────┘  └──────────────┘  └──────────────┘ │
│         │                  │                  │          │
│         ▼                  ▼                  ▼          │
│  ┌──────────────────────────────────────────────────┐  │
│  │         Thread-Safe Storage                       │  │
│  │  (sync.Map + sync.RWMutex)                       │  │
│  └──────────────────────────────────────────────────┘  │
│                          │                               │
│                          ▼                               │
│  ┌──────────────────────────────────────────────────┐  │
│  │      Underlying context.Context                   │  │
│  │  (Cancellation, Deadlines, Values)               │  │
│  └──────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────┘

Type System

Config[T comparable]
    │
    ├─ MapManage[T] interface
    │   ├─ Clean()
    │   ├─ Load(key T)
    │   ├─ Store(key T, val interface{})
    │   ├─ Delete(key T)
    │   ├─ LoadOrStore(key T, val interface{})
    │   └─ LoadAndDelete(key T)
    │
    ├─ Context interface
    │   └─ GetContext() context.Context
    │
    ├─ context.Context (embedded)
    │   ├─ Deadline()
    │   ├─ Done()
    │   ├─ Err()
    │   └─ Value(key interface{})
    │
    └─ Additional methods
        ├─ SetContext(ctx FuncContext)
        ├─ Clone(ctx context.Context)
        ├─ Merge(cfg Config[T])
        ├─ Walk(fct FuncWalk[T])
        └─ WalkLimit(fct FuncWalk[T], keys...)

---

Installation

go get github.com/nabbar/golib/context

For Gin integration:

go get github.com/nabbar/golib/context/gin

---

Quick Start

Basic Usage

package main

import (
    "fmt"
    libctx "github.com/nabbar/golib/context"
)

func main() {
    // Create a new config with string keys
    cfg := libctx.New[string](nil)
    
    // Store values
    cfg.Store("user", "john_doe")
    cfg.Store("role", "admin")
    cfg.Store("count", 42)
    
    // Load values
    user, ok := cfg.Load("user")
    if ok {
        fmt.Printf("User: %s\n", user.(string))
    }
    
    // Iterate over all values
    cfg.Walk(func(key string, val interface{}) bool {
        fmt.Printf("%s: %v\n", key, val)
        return true
    })
}

With Custom Key Types

type ConfigKey string

const (
    KeyDatabase ConfigKey = "database"
    KeyCache    ConfigKey = "cache"
    KeyAPI      ConfigKey = "api"
)

cfg := libctx.New[ConfigKey](nil)
cfg.Store(KeyDatabase, dbConnection)
cfg.Store(KeyCache, cacheClient)

// Type-safe access
if db, ok := cfg.Load(KeyDatabase); ok {
    // Use database connection
}

With Context Cancellation

ctx, cancel := context.WithCancel(context.Background())
defer cancel()

cfg := libctx.New[string](func() context.Context {
    return ctx
})

cfg.Store("key", "value")

// When context is cancelled, cleanup occurs
select {
case <-cfg.Done():
    fmt.Println("Context cancelled")
}

---

Core Concepts

Config Interface

The Config[T] interface extends context.Context with key-value storage:

type Config[T comparable] interface {
    context.Context
    MapManage[T]
    Context
    
    SetContext(ctx FuncContext)
    Clone(ctx context.Context) Config[T]
    Merge(cfg Config[T]) bool
    Walk(fct FuncWalk[T]) bool
    WalkLimit(fct FuncWalk[T], validKeys ...T) bool
}

MapManage Interface

Thread-safe map operations:

type MapManage[T comparable] interface {
    Clean()
    Load(key T) (val interface{}, ok bool)
    Store(key T, cfg interface{})
    Delete(key T)
    LoadOrStore(key T, cfg interface{}) (val interface{}, loaded bool)
    LoadAndDelete(key T) (val interface{}, loaded bool)
}

Function Types

// FuncContext provides the underlying context
type FuncContext func() context.Context

// FuncWalk is called for each key-value pair during iteration
type FuncWalk[T comparable] func(key T, val interface{}) bool

---

Operations

Store and Load

cfg := libctx.New[string](nil)

// Store a value
cfg.Store("key", "value")

// Load a value
if val, ok := cfg.Load("key"); ok {
    fmt.Println(val.(string))
}

// Store nil removes the key
cfg.Store("key", nil)

Atomic Operations

// LoadOrStore: load existing or store new
val, loaded := cfg.LoadOrStore("counter", 0)
if loaded {
    fmt.Println("Found existing:", val)
} else {
    fmt.Println("Stored new:", val)
}

// LoadAndDelete: retrieve and remove in one operation
if val, ok := cfg.LoadAndDelete("temporary"); ok {
    fmt.Println("Removed:", val)
}

Clone

// Create independent copy
original := libctx.New[string](nil)
original.Store("key1", "value1")
original.Store("key2", "value2")

clone := original.Clone(nil)
clone.Store("key3", "value3")

// original doesn't have key3
// clone has key1, key2, and key3

Merge

cfg1 := libctx.New[string](nil)
cfg1.Store("a", 1)

cfg2 := libctx.New[string](nil)
cfg2.Store("b", 2)

// Merge cfg2 into cfg1
if cfg1.Merge(cfg2) {
    // cfg1 now has both "a" and "b"
}

Walk

// Iterate over all keys
cfg.Walk(func(key string, val interface{}) bool {
    fmt.Printf("%s: %v\n", key, val)
    return true // continue iteration
})

// Iterate over specific keys only
cfg.WalkLimit(func(key string, val interface{}) bool {
    fmt.Printf("%s: %v\n", key, val)
    return true
}, "key1", "key2", "key3")

---

Performance

Memory Characteristics

• Config Instance: ~128 bytes (base)
• Per Entry: ~48 bytes overhead (sync.Map entry)
• RWMutex: 24 bytes
• Total per Config: ~152 bytes + (entries × 48 bytes)

Thread Safety

All operations are thread-safe through:

• sync.Map: Lock-free reads for most operations
• sync.RWMutex: Protects context function updates
• Atomic Guarantees: LoadOrStore, LoadAndDelete are atomic

Performance Benchmarks

Operation	Time	Allocations	Notes
New()	~200ns	1	One-time initialization
Store()	~100ns	0-1	Amortized, may allocate
Load()	~50ns	0	Lock-free read
LoadOrStore()	~150ns	0-1	Atomic operation
Walk()	~5µs	0	For 100 entries
Clone()	~10µs	100+	Depends on entry count
Merge()	~8µs	0-50	Depends on source size

Benchmarks on AMD64, Go 1.21

Concurrency

• Read Performance: Excellent (lock-free with sync.Map)
• Write Performance: Good (optimized for concurrent writes)
• Mixed Workload: Very good (sync.Map optimized for this)
• Contention: Low (minimal lock contention)

---

Use Cases

Application Configuration

type AppConfig struct {
    Database string
    CacheURL string
    APIKey   string
}

cfg := libctx.New[string](nil)
cfg.Store("app", AppConfig{
    Database: "postgres://...",
    CacheURL: "redis://...",
    APIKey:   "secret",
})

Request Scoped Data (HTTP)

func middleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        cfg := libctx.New[string](r.Context)
        cfg.Store("user_id", getUserID(r))
        cfg.Store("trace_id", generateTraceID())
        
        // Pass to next handler
        next.ServeHTTP(w, r.WithContext(cfg))
    })
}

Service Dependencies

type Services struct {
    DB    *sql.DB
    Cache *redis.Client
    Queue *amqp.Channel
}

cfg := libctx.New[string](nil)
cfg.Store("services", &Services{
    DB:    db,
    Cache: cache,
    Queue: queue,
})

Multi-Tenant Applications

cfg := libctx.New[string](nil)
cfg.Store("tenant_id", "tenant-123")
cfg.Store("tenant_config", tenantConfig)
cfg.Store("tenant_db", tenantDB)

Testing and Mocking

func TestHandler(t *testing.T) {
    cfg := libctx.New[string](nil)
    cfg.Store("db", mockDB)
    cfg.Store("cache", mockCache)
    
    // Test with mocked dependencies
    handler(cfg)
}

---

Advanced Usage

Context Propagation

func parent() {
    cfg := libctx.New[string](nil)
    cfg.Store("parent_data", "value")
    
    child(cfg)
}

func child(cfg libctx.Config[string]) {
    // Access parent data
    if val, ok := cfg.Load("parent_data"); ok {
        fmt.Println(val)
    }
    
    // Add child-specific data
    cfg.Store("child_data", "child_value")
}

Configuration Layers

// Base configuration
base := libctx.New[string](nil)
base.Store("env", "production")
base.Store("debug", false)

// Environment-specific overrides
envCfg := libctx.New[string](nil)
envCfg.Store("db_host", "prod-db.example.com")

// Merge layers
base.Merge(envCfg)

Cleanup Pattern

cfg := libctx.New[string](nil)

// Store resources
cfg.Store("db", dbConn)
cfg.Store("file", fileHandle)

// Cleanup
defer func() {
    cfg.Walk(func(key string, val interface{}) bool {
        switch v := val.(type) {
        case io.Closer:
            v.Close()
        }
        return true
    })
    cfg.Clean()
}()

---

Gin Integration

The context/gin sub-package provides seamless integration with the Gin web framework, offering a thin wrapper around Gin's context with additional features.

Installation

go get github.com/nabbar/golib/context/gin

Features

• ✅ Full context.Context compatibility - Implements standard context.Context
• ✅ Gin context access - Direct access to underlying gin.Context
• ✅ Type-safe getters - Convenient methods for common types
• ✅ Signal handling - Cancel context on OS signals (SIGTERM, SIGINT, etc.)
• ✅ Logger integration - Built-in logging support
• ✅ Request-scoped storage - Store and retrieve request-specific data
• ✅ Zero additional overhead - Thin wrapper around Gin context

GinTonic Interface

type GinTonic interface {
    context.Context
    
    // Gin integration
    GinContext() *gin.Context
    CancelOnSignal(s ...os.Signal)
    
    // Value storage
    Set(key any, value any)
    Get(key any) (value any, exists bool)
    MustGet(key any) any
    
    // Type-safe getters
    GetString(key any) string
    GetBool(key any) bool
    GetInt(key any) int
    GetInt64(key any) int64
    GetFloat64(key any) float64
    GetTime(key any) time.Time
    GetDuration(key any) time.Duration
    GetStringSlice(key any) []string
    GetStringMap(key any) map[string]any
    GetStringMapString(key any) map[string]string
    GetStringMapStringSlice(key any) map[string][]string
    
    // Logger
    SetLogger(log liblog.FuncLog)
}

Basic Usage

import (
    "github.com/gin-gonic/gin"
    ginlib "github.com/nabbar/golib/context/gin"
)

func main() {
    r := gin.Default()
    
    r.GET("/user/:id", func(c *gin.Context) {
        // Create GinTonic context
        gtx := ginlib.New(c, nil)
        
        // Store request-specific data
        gtx.Set("user_id", c.Param("id"))
        gtx.Set("request_time", time.Now())
        
        // Type-safe retrieval
        userID := gtx.GetString("user_id")
        reqTime := gtx.GetTime("request_time")
        
        c.JSON(200, gin.H{
            "user_id": userID,
            "timestamp": reqTime,
        })
    })
    
    r.Run(":8080")
}

Middleware Pattern

func ContextMiddleware() gin.HandlerFunc {
    return func(c *gin.Context) {
        gtx := ginlib.New(c, nil)
        
        // Store common request data
        gtx.Set("request_id", generateID())
        gtx.Set("user", getCurrentUser(c))
        gtx.Set("start_time", time.Now())
        
        // Continue to next handler
        c.Next()
        
        // Log request duration
        duration := time.Since(gtx.GetTime("start_time"))
        log.Printf("Request took %v", duration)
    }
}

r.Use(ContextMiddleware())

Signal Handling

func gracefulShutdown(c *gin.Context) {
    gtx := ginlib.New(c, nil)
    
    // Cancel context on SIGTERM or SIGINT
    gtx.CancelOnSignal(syscall.SIGTERM, syscall.SIGINT)
    
    select {
    case <-gtx.Done():
        log.Println("Context cancelled by signal")
        return
    case <-processRequest(gtx):
        log.Println("Request completed")
    }
}

Type-Safe Getters

func handler(c *gin.Context) {
    gtx := ginlib.New(c, nil)
    
    // Store various types
    gtx.Set("count", 42)
    gtx.Set("enabled", true)
    gtx.Set("ratio", 3.14)
    gtx.Set("tags", []string{"go", "gin", "web"})
    
    // Type-safe retrieval (returns zero value if not found)
    count := gtx.GetInt("count")           // 42
    enabled := gtx.GetBool("enabled")       // true
    ratio := gtx.GetFloat64("ratio")        // 3.14
    tags := gtx.GetStringSlice("tags")      // ["go", "gin", "web"]
    
    // Use MustGet if you want to panic on missing keys
    value := gtx.MustGet("required_key") // panics if not found
}

Logger Integration

import (
    ginlib "github.com/nabbar/golib/context/gin"
    liblog "github.com/nabbar/golib/logger"
)

func handler(c *gin.Context) {
    // Create logger function
    logger := func() liblog.Logger {
        return liblog.New(nil)
    }
    
    // Create GinTonic with logger
    gtx := ginlib.New(c, logger)
    
    // Logger is now available to components
    gtx.Set("user", "alice")
}

Testing

import (
    "testing"
    "net/http/httptest"
    
    "github.com/gin-gonic/gin"
    ginlib "github.com/nabbar/golib/context/gin"
)

func TestHandler(t *testing.T) {
    gin.SetMode(gin.TestMode)
    w := httptest.NewRecorder()
    c, _ := gin.CreateTestContext(w)
    
    gtx := ginlib.New(c, nil)
    gtx.Set("test_key", "test_value")
    
    if val := gtx.GetString("test_key"); val != "test_value" {
        t.Errorf("Expected 'test_value', got '%s'", val)
    }
}

---

Best Practices

1. Use Typed Keys

type ContextKey string

const (
    KeyUser    ContextKey = "user"
    KeySession ContextKey = "session"
)

cfg := libctx.New[ContextKey](nil)
cfg.Store(KeyUser, user)

2. Initialize with Parent Context

cfg := libctx.New[string](func() context.Context {
    return parentCtx
})

3. Check Load Results

if val, ok := cfg.Load("key"); ok {
    // Use val
} else {
    // Handle missing key
}

4. Use Type Assertions Safely

if val, ok := cfg.Load("count"); ok {
    if count, ok := val.(int); ok {
        fmt.Println(count)
    }
}

5. Clean Up Resources

defer cfg.Clean() // Remove all entries

6. Clone for Independence

// When you need isolated storage
clone := cfg.Clone(nil)
clone.Store("isolated_key", "value")

---

Testing

Comprehensive testing documentation is available in TESTING.md.

Quick Test:

cd context
go test -v -cover

With Race Detection:

CGO_ENABLED=1 go test -race -v

Test Metrics:

• 60+ test specifications

• 90% code coverage

• Ginkgo v2 + Gomega framework
• Full concurrency testing

---

Contributing

Contributions are welcome! Please follow these guidelines:

Code Contributions

• Do not use AI to generate package implementation code
• AI may assist with tests, documentation, and bug fixing
• All contributions must pass existing tests
• Maintain or improve test coverage
• Follow existing code style and patterns

Documentation

• Update README.md for new features
• Add examples for common use cases
• Keep TESTING.md synchronized with test changes
• Document all public APIs with GoDoc comments

Testing

• Write tests for all new features
• Test edge cases and error conditions
• Verify thread safety when applicable
• Add comments explaining complex test scenarios

Pull Requests

• Provide clear description of changes
• Reference related issues
• Include test results
• Update documentation

See CONTRIBUTING.md for detailed guidelines.

---

Future Enhancements

Potential improvements for future versions:

Performance Optimizations

• Custom memory pool for frequent allocations
• Batch operations for multiple keys
• Streaming walk operations for large datasets
• Copy-on-write optimization for cloning

Enhanced Features

• Typed value getters with automatic type conversion
• JSON/YAML serialization of stored values
• Expiration/TTL support for stored values
• Event hooks for Store/Delete operations
• Structured logging integration

Additional Integrations

• Echo framework support
• Chi router integration
• gRPC metadata integration
• Fiber framework support

Developer Experience

• Code generation for type-safe wrappers
• Visual debugging tools
• Performance profiling helpers
• Better error messages with context

Suggestions and contributions are welcome via GitHub issues.

---

Related Documentation

Go Standard Library

• context - Standard context package
• sync.Map - Concurrent-safe map
• sync.RWMutex - Read-write mutex

Related Golib Packages

• config - Application configuration (uses this package)
• atomic - Atomic operations

External Libraries

• Gin - Web framework (gin sub-package)
• Ginkgo Testing - BDD testing framework
• Gomega Matchers - Matcher library for tests

---

License

MIT License - See LICENSE file for details.

Copyright (c) 2019 Nicolas JUHEL

---

Resources

• Issues: GitHub Issues
• Documentation: GoDoc
• Testing Guide: TESTING.md
• Gin Integration: gin/README.md
• Contributing: CONTRIBUTING.md
• Source Code: GitHub Repository

---

This package is part of the golib project.