Is the map stream-safe in Go?

In Go, reading from a map is not thread-safe if a write occurs simultaneously. To safely read from a map in a multithreaded environment, synchronization is needed, for example, using sync.RWMutex for locking during read and write, or using sync.Map, which is specifically designed for concurrent access.

Example with sync.RWMutex:

import (
    "sync"
)

var (
    m  = make(map[string]int)
    mu sync.RWMutex
)

func read(key string) (int, bool) {
    mu.RLock()         // lock for reading
    defer mu.RUnlock() // unlock
    val, ok := m[key]
    return val, ok
}

func write(key string, val int) {
    mu.Lock()         // lock for writing
    defer mu.Unlock() // unlock
    m[key] = val
}

Or use sync.Map:

import "sync"

var m sync.Map

func read(key string) (interface{}, bool) {
    return m.Load(key)
}

func write(key string, val interface{}) {
    m.Store(key, val)
}

sync.Map is convenient when there are many concurrent operations, but it has some performance and API considerations.