{"id":1952,"date":"2020-04-08T11:41:31","date_gmt":"2020-04-08T11:41:31","guid":{"rendered":"https:\/\/golangbyexamples.com\/?p=1952"},"modified":"2021-01-05T23:07:40","modified_gmt":"2021-01-05T17:37:40","slug":"function-golang-complete-guide","status":"publish","type":"post","link":"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/","title":{"rendered":"Function in Go (Golang)"},"content":{"rendered":"\n<p class=\"has-medium-font-size\">This is the&nbsp; chapter 8 of the golang comprehensive tutorial series. Refer to this link for other chapters of the series \u2013&nbsp;<a href=\"https:\/\/golangbyexamples.com\/golang-comprehensive-tutorial\/\">Golang Comprehensive Tutorial Series<\/a><\/p>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Next Tutorial<\/strong>&nbsp;\u2013&nbsp;<a href=\"https:\/\/golangbyexamples.com\/constant-golang\/\">Constants<\/a><br><strong>Previous Tutorial<\/strong>&nbsp;\u2013<a href=\"https:\/\/golangbyexamples.com\/all-basic-data-types-golang\/\">All basic data types<\/a><br><\/p>\n\n\n\n<p class=\"has-medium-font-size\">Now let\u2019s check out the current tutorial. Below is the table of contents for current tutorial.<\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_17 counter-hierarchy counter-decimal ez-toc-light-blue\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" style=\"display: none;\"><i class=\"ez-toc-glyphicon ez-toc-icon-toggle\"><\/i><\/a><\/span><\/div>\n<nav><ul class=\"ez-toc-list ez-toc-list-level-1\"><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Overview\" title=\"Overview\">Overview<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Signature_of_a_function\" title=\"Signature of a function\">Signature of a function<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Calling_a_function\" title=\"Calling a function\">Calling a function<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Function_Parameters\" title=\"Function Parameters\">Function Parameters<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Return_Values\" title=\"Return Values\">Return Values<\/a><ul class=\"ez-toc-list-level-2\"><li class=\"ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Named_Return_Values\" title=\"Named Return Values\">Named Return Values<\/a><\/li><\/ul><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Function_Usages\" title=\"Function Usages\">Function Usages<\/a><ul class=\"ez-toc-list-level-2\"><li class=\"ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Generic_Usage\" title=\"Generic Usage\">Generic Usage<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Function_as_Type\" title=\"Function as&nbsp; Type\">Function as&nbsp; Type<\/a><ul class=\"ez-toc-list-level-3\"><li class=\"ez-toc-heading-level-3\"><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Function_as_User_Defined_Type\" title=\"Function as User Defined Type\">Function as User Defined Type<\/a><\/li><\/ul><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Function_as_values_or_Anonymous_functions\" title=\"Function as values (or Anonymous functions)\">Function as values (or Anonymous functions)<\/a><\/li><\/ul><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Special_Usages_of_Function\" title=\"Special Usages of Function\">Special Usages of Function<\/a><ul class=\"ez-toc-list-level-2\"><li class=\"ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Function_Closures\" title=\"Function Closures\">Function Closures<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Higher_Order_Function\" title=\"Higher Order Function\">Higher Order Function<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#IIF_or_Immediately_Invoked_Function\" title=\"IIF or Immediately Invoked Function\">IIF or Immediately Invoked Function<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Variadic_Function\" title=\"Variadic Function\">Variadic Function<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Methods\" title=\"Methods\">Methods<\/a><\/li><\/ul><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-1\"><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/#Conclusion\" title=\"Conclusion\">Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Overview\"><\/span><strong>Overview<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<p class=\"has-medium-font-size\"><br>A function is a group of statements that perform a specific task. In GO functions are first-order variables. They can be passed around like any other variable.&nbsp;<\/p>\n\n\n\n<p class=\"has-medium-font-size\">Some point worth noting about a function name<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>A function name cannot begin with a number<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>The function name is case sensitive. Hence sum, Sum,&nbsp; SUM are different functions.&nbsp;<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>A function whose name starts with a capital letter will be exported outside its package and can be called from other packages. A function whose name starts with lowercase letters will not be exported and it&#8217;s only visible within its package.<\/li><\/ul>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Signature_of_a_function\"><\/span><strong>Signature of a function<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func func_name(input_parameters) return_values{\n  \/\/body\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">A function in golang<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Declared using <strong>func<\/strong> keyword<\/li><li>It has a name<\/li><li>Comma-separated zero or more input parameters<\/li><li>Comma-separated zero or more return values<\/li><li>Function body<\/li><li>Can return multiple values<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">An example of a function. The below function is<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Has the name <strong>&#8220;sum&#8221;<\/strong><\/li><li>Accept two arguments of int type<\/li><li>Return a single value of type int<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func sum(a int, b int) int {\n  return a + b \n}<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Calling_a_function\"><\/span><strong>Calling a function<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<p class=\"has-medium-font-size\">A function in Go can be called in go as below<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">results := sum(2, 3)<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">Some points to note about calling a function<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>If the function of some other package is being called then it is necessary to prefix the package name. Also please note that across packages only those function can be called which are exported meaning whose name start with capital letter<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>With in the same package the function can directly be called using its name suffixed by ()<\/li><\/ul>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Function_Parameters\"><\/span><strong>Function Parameters<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>As mentioned above function can have zero or more arguments.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>type for the consecutive same types can be specified only once. For example above sum function can also be written as<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func sum(a, b int)<\/code><\/pre>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>A copy of all the arguments is made while calling a function.<\/li><\/ul>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Return_Values\"><\/span><strong>Return Values<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>As mentioned above a function can have one or more return values. Assume there is a function sum_avg that returns two values: Sum and Average. Example of multiple return values<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func sum_avg(a, b int) (int, int)<\/code><\/pre>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>As a convention error is returned as the last argument in a function. Example<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func sum(a, b int) (int, error)<\/code><\/pre>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Collecting multiple return values in the caller function. In below example<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">result, err := sum(2, 3) <\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Named_Return_Values\"><\/span><strong>Named Return Values<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">A go function can have named return values. With named return values , the return values did not need to be initialised in the function<strong>. <\/strong>The named variables are specified in the signature itself. Without named values,&nbsp; only return type is specified. It is also ok to name some of the return values. For other return values only type can be specified.&nbsp;<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>See example below: <strong>result<\/strong> is the named return value<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func sum(a, b int) (result int)<\/code><\/pre>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>With named return values, type of the consecutive same types can be specified only once<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-\">func sum_avg(a, b int) (sum, avg int)<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Function_Usages\"><\/span><strong>Function Usages<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Generic usage<\/li><li>Function as Type<\/li><li>Function as Values<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">The difference between function as type and function as values is that in type we only use the function signature whereas in function as value signature along with the body is used.&nbsp; Let&#8217;s see each of this in detail so it is more clear<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Generic_Usage\"><\/span><strong>Generic Usage<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">Below is an example of the general usage of a function. We have a function sum in the below example which takes in two ints as input arguments and returns the sum.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    res := sum(2, 3)\n    fmt.Println(res)\n}\n\nfunc sum(a, b int) int {\n    return a + b\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">5<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Function_as_Type\"><\/span><strong>Function as&nbsp; Type<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">In go function is also a type.&nbsp;Two function will be of same type if<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>They have the same number of arguments with each argument is&nbsp;of the same type<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>They have same number of return values and each return value is of same type.&nbsp;<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">Function type is useful in&nbsp;<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>In the case of&nbsp;higher-order functions as&nbsp;we have seen in the above example. The argument and return type is specified using function type<\/li><li>In the case of defining interfaces in go as in the interface, only the function type is specified.&nbsp;Whatever implements this interface has to define a function of the same type<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">Let&#8217;s see an example of function type in the interface. Notice that the interface <strong>shape <\/strong>only defines the type of function<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">area() int\ngetType() string<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Code:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\nimport \"fmt\"\nfunc main() {\n    var shapes []shape\n    s := &square{side: 2}\n    shapes = append(shapes, s)\n    r := &rectangle{length: 2, breath: 3}\n    shapes = append(shapes, r)\n    for _, shape := range shapes {\n        fmt.Printf(\"Type: %s, Area %d\\n\", shape.getType(), shape.area())\n    }\n}\ntype shape interface {\n    area() int\n    getType() string\n}\ntype rectangle struct {\n    length int\n    breath int\n}\nfunc (r *rectangle) area() int {\n    return r.length * r.breath\n}\nfunc (r *rectangle) getType() string {\n    return \"rectangle\"\n}\ntype square struct {\n    side int\n}\nfunc (s *square) area() int {\n    return s.side * s.side\n}\nfunc (s *square) getType() string {\n    return \"square\"\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-\">Type: square, Area 4\nType: rectangle, Area 6<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Function_as_User_Defined_Type\"><\/span><strong>Function as User Defined Type<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<p class=\"has-medium-font-size\">Function as user defined type can be declared using the type keyword<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    areaF := getAreaFunc()\n    print(3, 4, areaF)\n}\n\ntype area func(int, int) int\n\nfunc print(x, y int, a area) {\n    fmt.Printf(\"Area is: %d\\n\", a(x, y))\n}\n\nfunc getAreaFunc() area {\n    return func(x, y int) int {\n        return x * y\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">12<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Function_as_values_or_Anonymous_functions\"><\/span><strong>Function as values (or Anonymous functions)<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">A function in Go is a first-order variable so it can be used as a value as well. It is also called as anonymous functions because a function is not named and can be assigned to a variable and passed around. <\/p>\n\n\n\n<p class=\"has-medium-font-size\">They are generally created for short term use or for limited functionality. See the below example. In this example variable<strong> max <\/strong>assigned a function. Since <strong>max<\/strong> is created by a function that is not named, it is an anonymous function.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nvar max = func(a, b int) int {\n    if a >= b {\n        return a\n    }\n    return b\n}\n\nfunc main() {\n    res := max(2, 3)\n    fmt.Println(res)\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-\">3<\/code><\/pre>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Special_Usages_of_Function\"><\/span><strong>Special Usages of Function<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Function_Closures\"><\/span><strong>Function Closures<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">Function closures are nothing but anonymous function which can access variables declared outside the function and also retain the current value between different function calls. Let&#8217;s see an example. In below case the <strong>count <\/strong>value is retained between different function calls of <strong>modulus<\/strong> function<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport (\n    \"fmt\"\n)\n\nfunc main() {\n    modulus := getModulus()\n    modulus(-1)\n    modulus(2)\n    modulus(-5)\n}\n\nfunc getModulus() func(int) int {\n    count := 0\n    return func(x int) int {\n        count = count + 1\n        fmt.Printf(\"modulus function called %d times\\n\", count)\n        if x < 0 {\n            x = x * -1\n        }\n        return x\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">modulus function called 1 times\nmodulus function called 2 times\nmodulus function called 3 times<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Higher_Order_Function\"><\/span><strong>Higher Order Function<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">Higher-order functions are those functions that either accept a function as a type or return function. Since the function is the first-order variable in Golang they can be passed around and also returned from some function and assigned to a variable. In below example<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li><strong>print<\/strong> function takes a function of type <strong>func(int, int) int <\/strong>as an argument<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li><strong>getAreafunc<\/strong> returns a function of type <strong>func(int, int) int<\/strong><\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    areaF := getAreaFunc()\n    print(3, 4, areaF)\n}\n\nfunc print(x, y int, area func(int, int) int) {\n    fmt.Printf(\"Area is: %d\\n\", area(x, y))\n}\n\nfunc getAreaFunc() func(int, int) int {\n    return func(x, y int) int {\n        return x * y\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">12<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"IIF_or_Immediately_Invoked_Function\"><\/span><strong>IIF or Immediately Invoked Function<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\"><strong>IIF or <\/strong>Immediately Invoked Function are those function which can be defined and executed at the same time.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    squareOf2 := func() int {\n        return 2 * 2\n    }()\n    fmt.Println(squareOf2)\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">4<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Use Cases of IIF functions<\/strong><\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>When you don't want to expose the logic of the function either within or outside the package. For eg let's say there is a function which is setting some value. You can encapsulate all the logic of setting in an IIF function. This function won't be available for calling either outside or within the package.<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Variadic_Function\"><\/span><strong>Variadic Function<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">In Go, a function that can accept a dynamic number of arguments is called a Variadic function. Below is the syntax for variadic function. Three dots are used as a prefix before type.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func add(numbers ...int)<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Code:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\nfunc main() {\n    fmt.Println(add(1, 2))\n    fmt.Println(add(1, 2, 3))\n    fmt.Println(add(1, 2, 3, 4))\n}\n\nfunc add(numbers ...int) int {\n    sum := 0\n    for _, num := range numbers {\n        sum += num\n    }\n    return sum\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">3\n6\n10<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Methods\"><\/span><strong>Methods<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">Method has a receiver argument. When you attach a function to a type, then that function becomes a method for that type. A receiver can be a struct or any other type. The method will have access to the properties of the receiver and can call the receiver's other methods.<\/p>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Function:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func some_func_name(arguments) return_values<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Method:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">func (receiver receiver_type) some_func_name(arguments) return_values<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">This is the only difference between function and method, but due to it they differ in terms of functionality they offer<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>A function can be used as first-order objects and can be passed around while methods cannot.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Methods can be used for chaining on the receiver while function cannot be used for the same.<\/li><\/ul>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>There can exist different methods with the same name with a different receiver, but there cannot exist two different functions with the same name in the same package.<\/li><\/ul>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span><strong>Conclusion<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<p class=\"has-medium-font-size\">This is all about function in golang. Hope you have liked this article. Please share feedback or mistakes\/improvements in comments.<\/p>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Next Tutorial<\/strong>&nbsp;\u2013&nbsp;<a href=\"https:\/\/golangbyexamples.com\/constant-golang\/\">Constants<\/a><br><strong>Previous Tutorial<\/strong>&nbsp;\u2013<a href=\"https:\/\/golangbyexamples.com\/all-basic-data-types-golang\/\">All basic data types<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This is the&nbsp; chapter 8 of the golang comprehensive tutorial series. Refer to this link for other chapters of the series \u2013&nbsp;Golang Comprehensive Tutorial Series Next Tutorial&nbsp;\u2013&nbsp;ConstantsPrevious Tutorial&nbsp;\u2013All basic data types Now&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","footnotes":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false},"categories":[1],"tags":[16,97,3,4,17],"class_list":["post-1952","post","type-post","status-publish","format-standard","hentry","category-tech","tag-complete","tag-function","tag-go","tag-golang","tag-guide"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Function in Go (Golang) - Welcome To Golang By Example<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/golangbyexamples.com\/function-golang-complete-guide\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Function in Go (Golang) - Welcome To Golang By Example\" \/>\n<meta property=\"og:description\" content=\"This is the&nbsp; chapter 8 of the golang comprehensive tutorial series. 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