Go Assignment Operators: When to Use `:=` vs. `=`?

Understanding Assignment Operators in Go: := vs. =

In Go, assignment can be done using two different operators: = and :=. While both operators perform assignment, they serve distinct purposes and have specific use cases.

= Operator

The = operator is primarily used for assignment. It assigns a value to an existing variable. For instance:

var foo int = 10
foo = 20

In this example, the variable foo is declared and assigned the value 10 using the var keyword. The subsequent line assigns a new value of 20 to foo using the = operator.

:= Operator

The := operator, on the other hand, is a combination of declaration and assignment. It is typically used to declare and initialize a new variable in a single statement. Consider the following example:

foo := 10

This line declares a new variable foo of type int and assigns the value 10 to it. The := operator simplifies the process by combining declaration and assignment into one step.

Use Cases

• Use the = operator when you are modifying the value of an existing variable.
• Use the := operator when declaring and initializing a new variable. This is particularly useful for local variables within functions or for declaring multiple variables with the same value.

Example

Consider the following function:

func multiply(a, b int) int {
  result := a * b
  return result
}

In this function, the := operator is used to declare and initialize a local variable result. The variable is then assigned the product of the two input parameters using the = operator. This combination of := and = operators allows for clear and concise code.

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