Unlock Go's Syntactic Sugar: Master Variadic Functions and := Assignment

Syntactic sugar, also called sugar-coated syntax, is a term coined by computer scientist Peter J. Landin to describe language features that do not add new functionality but make code easier to write and read.

1. Variadic parameters

In Go, three dots ( ...) denote a variadic parameter, allowing a function to accept any number of arguments of the same type.

func print(values ...string) { // can accept any number of string arguments
    for _, v := range values {
        fmt.Println("---> ", v)
    }
}

func main() {
    values := []string{"abc", "def", "hig", "klm"}
    print(values...)
}

Another example shows two ways to implement a variadic‑like function:

func myFunc1(args ...int) {
    for _, arg := range args {
        fmt.Println(arg)
    }
}

func myFunc2(args []int) {
    for _, arg := range args {
        fmt.Println(arg)
    }
}

myFunc1

uses Go's syntactic sugar; myFunc2 achieves the same effect but requires the caller to construct a slice, making the call more verbose.

2. Assignment syntax sugar

The := operator combines declaration, assignment, and type inference in a single step.

// First method
var number1, number2, number3 int
number1, number2, number3 = 1, 2, 3

// Second method
var number1, number2, number3 = 1, 2, 3

// Third method
number1, number2, number3 := 1, 2, 3

Precautions

:= can be used only when at least one variable on the left side is newly defined.

:= performs only semantic checks; it can be used inside loops, behaving like = after the first iteration.

Both := and = require the number of variables and values to match exactly; no truncation occurs.

Special cases: map, channel, and type assertions can return one or two values.

When a map key does not exist, the operation returns the zero value and false; otherwise it returns true.

When a channel is closed, receiving returns the zero value and false; otherwise it returns true.