- Basic Function Syntax
func functionName(parameters) returnType { // function body } Example:
func greet(name string) string { return "Hello, " + name } - Calling a Function
message := greet("Alice") fmt.Println(message) // Output: Hello, Alice - Multiple Parameters
func add(a int, b int) int { return a + b } Shortcut: Same type for multiple parameters:
func add(a, b int) int { return a + b } - Multiple Return Values
func divide(dividend, divisor float64) (float64, string) { if divisor == 0 { return 0, "Error: Division by zero" } return dividend / divisor, "Success" } result, status := divide(10, 2) - Named Return Values You can give names to return values — useful in longer functions.
func getFullName() (firstName, lastName string) { firstName = "John" lastName = "Doe" return // implicit return } - Variadic Functions (accept any number of arguments)
func sum(nums ...int) int { total := 0 for _, num := range nums { total += num } return total } sum := sum(1, 2, 3, 4, 5) // Output: 15 - Anonymous Functions Functions without names, used for short tasks or inline.
func() { fmt.Println("I am anonymous") }() Or assign to a variable:
greet := func(name string) string { return "Hello, " + name } fmt.Println(greet("Bob")) - Closures (Function with Access to Outer Variables)
func counter() func() int { count := 0 return func() int { count++ return count } } next := counter() fmt.Println(next()) // 1 fmt.Println(next()) // 2 - Function as Parameter
func process(name string, f func(string) string) string { return f(name) } func shout(s string) string { return strings.ToUpper(s) } result := process("hello", shout) - Scope in Go
- Local scope: Variables declared inside a function are only accessible there.
- Global scope: Variables declared outside of all functions are accessible everywhere in the same package.
- Block scope: Variables inside {} are scoped to that block.
var globalVar = "I’m global" func example() { localVar := "I’m local" fmt.Println(globalVar, localVar) } - Return Early (Best Practice) Avoid deep nesting using early returns:
func login(user string) string { if user == "" { return "No user provided" } return "Welcome " + user } - Recursive Function A function that calls itself:
func factorial(n int) int { if n == 0 { return 1 } return n * factorial(n-1) } 
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