Atomic Operations (sync/atomic)

A mutex is suited to protecting a block of code, but it's overkill for a single-word update like incrementing a page-view counter. The sync/atomic package exposes hardware-level read-modify-write instructions that finish in one indivisible step, so two goroutines hammering the same int64 can't tear the value apart. This lesson covers when atomic operations beat a mutex, the two API flavours (function form and the newer type form), the compare-and-swap pattern for lock-free state machines, and the alignment trap that causes panics on 32-bit builds.