Array: Fixed length, value type (copying copies entire array).

Slice: Dynamic length, reference type (pointer to underlying array).

Maps are not safe for concurrent use. Use sync.Mutex to lock before access, or use sync.Map for specific high-concurrency read-heavy cases.

Go favors Composition. Embedding a struct allows utilizing its methods, but it's not "is-a" relationship, it's "has-a" with syntax sugar.

type Car struct { Engine } // Car promotes methods of Engine

go mod init creates a new module. go.mod tracks dependencies and versions, replacing the old GOPATH system.

Schedules a function call to be run after the surrounding function returns. Executed in LIFO order. Common for cleanup (closing files, unlocking mutexes).

Panic: Stops normal execution, unwinds stack, runs deferred functions. Used for unrecoverable errors.

Recover: Regains control of a panicking goroutine. Only works inside defer.

The CPU reads data in word-sized chunks. Go struct fields are aligned to these boundaries. Proper ordering of struct fields (largest to smallest) can save memory by reducing padding.

Used to carry deadlines, cancellation signals, and request-scoped values across API boundaries and between processes.

Determines if variables should be on stack or heap. Heap allocation causes GC pressure. Optimization: Keep variables on stack (don't return pointers to local vars if not needed) to reduce GC overhead.

Use golang.org/x/time/rate.Limiter or a Token Bucket implementation. Call Wait(ctx) before making a request.