Understanding Go's sync Package: Map

The sync package in Go provides the Map type, a concurrent-safe map implementation.

Table of Contents

1. Introduction to Map
2. Usage of Map
3. Use Cases
4. Common Pitfalls
5. Best Practices
6. Resources

Introduction to Map

sync.Map is a concurrent map type with amortized-constant-time loads, stores, and deletes.

Usage of Map

var m sync.Map

func main() {
    m.Store("hello", "world")
    if value, ok := m.Load("hello"); ok {
        fmt.Println(value)  // Output: world
    }
}

Examples and tests

See package

Use Cases

The Map type is optimized for two common use cases

• When the entry for a given key is only ever written once but read many times, as in caches that only grow.
• when multiple goroutines read, write, and overwrite entries for disjoint sets of keys.

In these two cases, use of a Map may significantly reduce lock contention compared to a Go map paired with a separate Mutex or RWMutex.

Common Pitfalls

• Not a general replacement for Go's built-in map type due to its specific performance characteristics.

Best Practices

• Prefer Go's built-in map type with proper locking for most use cases.

Resources

• Official Go Documentation on sync.Map
• Effective Go