Defer

defer schedules a function call to run just before the surrounding function returns — no matter how it returns (normally, early, or with a panic).

It’s one of Go’s most practical features. You’ll use it constantly for cleanup: closing files, releasing locks, stopping timers. Write the cleanup right next to the setup, and defer handles the timing.

One important detail: the arguments to a deferred call are evaluated immediately when defer is encountered — only the execution is delayed.

Try it — run the example. Notice that “world” prints after “hello”, even though defer appears first in the code.