Anonymous Functions in Go

In this tutorial, we are going to discuss anonymous functions in the Go language. Go language provides a special feature known as an anonymous function.

An anonymous function is a function that doesn’t contain any name. It is useful when you want to create an inline function.

In the Go language, an anonymous function can form a closure. An anonymous function is also known as function literal.

Declaring Anonymous Functions

Declaration syntax for anonymous function is pretty straightforward. It is no different in syntax than a regular function.

Syntax

func(parameter_list)(return_type){
// code 
// Use return statement if return_type are given if return_type 
// is not given, then do not use return statement 
return 
}()

package main

import "fmt"

func main() {
    func() {
        fmt.Println("Welcome to Waytoeasylearn..!!")
    }()
}

Welcome to Waytoeasylearn..!!

Run in playground

In Go language, you are allowed to assign an anonymous function to a variable.

When you assign a function to a variable, then the type of the variable is of function type and you can call that variable like a function call as shown in the below example.

package main

import "fmt"

func main() {
    value := func() {
        fmt.Println("Welcome to Waytoeasylearn..!!")
    }
    value()
}

Run in playground

Please note that you can also pass arguments in the anonymous function.

package main

import "fmt"

func main() {
    func(message string) {
        fmt.Println(message)
    }("Welcome to Waytoeasylearn..!!")
}

Run in playground

You can also pass an anonymous function as an argument into other function.

package main 
 
import "fmt"

func print(i func(p, q string)string){ 
    fmt.Println(i ("Welcome ", "to ")) 
} 

func main() { 
    value:= func(p, q string) string{ 
        return p + q + "Waytoeasylearn..!!"
    } 
    print(value) 
}

Run in playground

You can also return an anonymous function from another function.

package main 

import "fmt"

func display() func(i, j string) string{ 
    myf := func(i, j string)string{ 
        return i + j + "Waytoeasylearn..!!"
    } 
    return myf 
} 

func main() { 
    value := display() 
    fmt.Println(value("Welcome ", "to ")) 
}

Run in playground

Please note that anonymous functions can accept inputs and return outputs, just as standard functions do.

Anonymous Functions in Go