...

The defer Keyword

Let’s learn what the defer keyword does.

We'll cover the following...

Deferred functions
Coding example
Let’s try our code

So far, we have seen defer in previous lessons, as well as in the implementations of the phone book application. But what does defer do? The defer keyword postpones the execution of a function until the surrounding function returns. Usually, defer is used in file I/O operations to keep the function call that closes an opened file close to the call that opened it. This helps to avoid the common programmer error where we forget to close a file—that we had opened earlier—just before the function exits.

Deferred functions

It is very important to remember that deferred functions are executed in last in, first out (LIFO) order after the surrounding function has been returned. Putting it simply, this means that if we defer function f1() first, function f2() second, and function f3() third in the same surrounding function, then when the surrounding function is about to return, function ...

Course Introduction

Introduction to Go

Basic Go Data Types

Composite Data Types

Reflection and Interfaces

Go Packages and Functions

Telling a UNIX System What to Do

Go Concurrency

Building Web Services

Working with TCP/IP and WebSocket

Working with REST APIs

Code Testing and Profiling

Working with gRPC

Go Generics

Conclusion

Appendix A—Go Garbage Collector

The defer Keyword

Deferred functions