How do you choose between mutexes and channels for concurrency?

Go's advice is "do not communicate by sharing memory; share memory by communicating", but both tools are legitimate.

• Use a mutex when protecting a small piece of shared state such as a counter, cache or struct field. It is simpler, cheaper and avoids goroutine leaks.

type SafeMap struct {
    mu sync.RWMutex
    m  map[string]int
}

func (s *SafeMap) Get(k string) int {
    s.mu.RLock()
    defer s.mu.RUnlock()
    return s.m[k]
}

• Use channels to transfer ownership of data, to build pipelines, to signal completion, or to coordinate a bounded worker pool. Channels give you synchronisation plus select-based multiplexing for free.

The trade-offs: channels are heavier and overuse leads to convoluted control flow. A mutex protects state but does not coordinate lifetimes. Never copy a mutex after first use, prefer sync.RWMutex for read-heavy data, keep critical sections small, and always run go test -race to catch data races.