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`sync/atomic` provides low-level atomic memory primitives for safe, lock-free access to shared integer and pointer values.

• Perform simple concurrent operations without using `Mutex`.
• Common ops: atomic add, load/store, compare-and-swap (CAS).

• You need very simple shared state, like counters, flags, or pointers.
• You want to avoid lock overhead for hot paths.
• You understand the memory-ordering implications (advanced topic).

package main
 
import (
    "fmt"
    "sync"
    "sync/atomic"
)
 
func main() {
    var n int64
    var wg sync.WaitGroup
 
    for i := 0; i < 100; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            atomic.AddInt64(&n, 1)
        }()
    }
 
    wg.Wait()
    fmt.Println(atomic.LoadInt64(&n))
}

• Prefer `sync.Mutex` for complex shared state (maps, slices, structs with multiple fields).
• For correctness, always use `atomic.Load*` / `atomic.Store*` instead of plain reads/writes.
• Do not mix atomic and non-atomic access to the same variable.

• sync.Mutex
• sync.RWMutex
• Race detector (-race)

• lock-free /ˌlɑːk ˈfriː/: không cần khóa
• atomic /əˈtɑːmɪk/: nguyên tử (trọn vẹn, không bị xen ngang)
• primitive /ˈprɪmətɪv/: thao tác/công cụ nền tảng
• overhead /ˈoʊvərhed/: chi phí phát sinh
• hot path /hɑːt pæθ/: đoạn code chạy rất thường xuyên
• implication /ˌɪmplɪˈkeɪʃən/: hệ quả
• memory ordering /ˈmeməri ˈɔːrdərɪŋ/: thứ tự bộ nhớ (khái niệm nâng cao)
• compare-and-swap (CAS) /kəmˈper ænd swɑːp/: so sánh và hoán đổi