What is defer keyword in Go language?

What is the defer keyword in Go language?

When writing programs, we often need to perform some cleanup or resource release work after a certain function or method is executed. At this time, the Go language provides a convenient mechanism. By using the defer keyword, these cleanup or resource release tasks can be postponed until the function or method returns. The

defer keyword is a syntactic sugar that is parsed at compile time. It delays the call of a function or method until the current function or method returns, thereby releasing resources or performing cleanup before the end of program execution. Purpose of work. The defer keyword can appear anywhere in a function or method, and there can be multiple defer statements, which are executed in reverse order.

defer func() {
// defer delayed execution code
}()

The defer statement in the example defines the function to be executed in an anonymous function, which can be Any function or method call. The left bracket after defer must immediately follow the defer keyword, and the right bracket must be at the end of the code to be executed, so as to ensure the correct syntax structure.

The defer keyword is used in more than just releasing resources or performing cleanup work. It can also be used to monitor the execution of functions or methods. Use defer to record the timestamps before and after the function or method is called. You can easily record the time it takes to execute the function or method.

func someFunction() {
start := time.Now() // Record starting time
defer func() {

elapsed := time.Since(start)
fmt.Printf("time taken by someFunction: %v

", elapsed)
}()

//The main logic of someFunction
}

In the above example, someFunction will output the time it took to execute after the execution returns. This monitors function or method performance The method is very practical and can help us better understand the performance bottlenecks of the program and make adjustments and improvements.

defer keyword can also be used in panic and recover processing. When the program panics, you can Restore the program to the normal state through the recover statement in the defer statement.

func someFunction() {
defer func() {

if err := recover(); err != nil {
  fmt.Println("panic occurred:", err)
}

}()

/ / The main logic of someFunction
}

In the above example, someFunction will output panic error information when panic occurs, so that we can handle program errors in a timely manner and keep the program running as normally as possible .

In summary, the defer keyword in Go language is used to postpone the execution of a certain function or method, handle resource release or cleanup work, monitor the execution of functions or methods, and handle panic and recovery, etc. A practical tool. It can not only improve the efficiency and performance of the program, but also improve the reliability and robustness of the program. Therefore, using the defer keyword is a very good choice when writing a program.

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