Function parameters in Go are a crucial aspect of writing flexible and reusable code. They allow you to pass data into functions, making your programs more dynamic and versatile.

Defining Function Parameters

In Go, function parameters are defined within parentheses after the function name. Each parameter consists of a name followed by its type.

func greet(name string) {
    fmt.Println("Hello,", name)
}

In this example, name is a parameter of type string.

Multiple Parameters

Go functions can have multiple parameters, separated by commas:

func calculateArea(width float64, height float64) float64 {
    return width * height
}

When parameters share the same type, you can omit the type for all but the last parameter:

func calculateArea(width, height float64) float64 {
    return width * height
}

Variadic Parameters

Go supports variadic functions, which can accept a variable number of arguments. Use an ellipsis (...) before the type to indicate a variadic parameter:

func sum(numbers ...int) int {
    total := 0
    for _, num := range numbers {
        total += num
    }
    return total
}

This function can be called with any number of integer arguments: sum(1, 2, 3) or sum(10, 20, 30, 40).

Passing Arguments

When calling a function, you pass arguments that correspond to the function's parameters:

greet("Alice")
area := calculateArea(5.0, 3.0)
total := sum(1, 2, 3, 4, 5)

Parameter Passing Behavior

Go uses pass-by-value for function parameters. This means that functions receive a copy of the argument's value, not a reference to the original variable.

For large structs or arrays, consider using pointers to avoid copying large amounts of data:

func modifyUser(u *User) {
    u.Name = "Modified"
}

Best Practices

Use descriptive parameter names to improve code readability.
Keep the number of parameters manageable. If a function requires many parameters, consider using a struct instead.
Use variadic parameters judiciously, as they can make function calls less clear.
When working with slices or maps, remember that they are reference types, so modifications within the function will affect the original data.

Related Concepts

To deepen your understanding of Go functions, explore these related topics:

By mastering function parameters in Go, you'll be able to create more flexible and powerful functions, enhancing your overall Go programming skills.