Go

Fixed-length value types, copying semantics, indexing, iteration, and their relationship to slices.

Slice descriptors, backing arrays, append/capacity, sharing, copying, and retention pitfalls.

Deferred calls, LIFO execution, argument evaluation, return interaction, and practical cleanup patterns.

Go context trees for cancellation, deadlines, timeouts, and request-scoped values, with lifecycle rules for passing and canceling contexts.

Waiting for a group of goroutines to finish with Add, Done, and Wait, including the counter lifecycle and common Add/Wait misuse.

A map of Go's shared-memory synchronization primitives: Mutex, RWMutex, Once, Cond, Map, Pool, WaitGroup, and atomic operations.

Go's specialized concurrent map, its intended workloads, read-optimized internal design, atomic map operations, and when a normal map plus mutex is clearer.

Temporary object reuse, GC interaction, per-P optimization, and when pooling helps.

How Go `select` waits on multiple channel operations, chooses among ready cases, uses `default`, handles nil channels, timeouts, and cancellation.

Exactly-once process-local initialization and its concurrency semantics.