In Go language, defer statements delay the execution of the function or method or an anonymous method until the nearby functions returns. Or in other words, defer function or method call arguments evaluate instantly, but they execute until the nearby functions returns. You can create a deferred method, or function, or anonymous function by using the defer keyword.

Syntax:

// Function
defer func func_name(parameter_list Type)return_type{
// Code
}

// Method
defer func (receiver Type) method_name(parameter_list){
// Code
}

defer func (parameter_list)(return_type){
// code
}()

Important Points:

• In Go language, multiple defer statements are allowed in the same program and they are executed in LIFO(Last-In, First-Out) order as shown in Example 2.
• In the defer statements, the arguments are evaluated when the defer statement executed, not when they called.
• Defer statements are generally used to ensure that the files are closed when your work is finished with them, or to close the channel, or to catch the panics in the program.

Let us discuss this concept with the help of an example:

Example 1:

Output:

Result:  1035
Hello!, GeeksforGeeks
Result:  1288

Explanation: In the above example we have two functions named as mul() and show() function. Where show() function call normally in the main() function, but we call mul() function in two different ways:

• First, we call mul function like the normal function, i.e, mul(23, 45) and executes when the function called(Output: Result : 1035 ).
• Second, we call mul() function as a defer function using defer keyword, i.e, defer mul(23, 56) and it executes(Output: Result: 1288 ) when all the surrounding methods return.

Example 2:

Output:

Start
Result:  20
Result:  90
End

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.