How Can I Declare Go Constants with Non-Compile-Time Expressions?

Declaring Const Variables with Non-Compile-Time Expressions

In Go, const variables must represent values that can be evaluated at compile time. As a result, attempts to initialize const variables using function calls will encounter errors. This is because functions are executed at runtime, not compile time.

The error message you received, "const initializer math.Pow10(3) is not a constant," indicates that the function math.Pow10(3) used to initialize KILO cannot be evaluated at compile time.

Workaround: Use Literal Values

To declare const variables with non-compile-time expressions, you must use literal values instead. For example, you can use an integer literal:

const Kilo = 1000

Or a floating-point literal:

const Kilo = 1e3

Using Variables

If you truly need to use a function to compute a value for a constant, you cannot store it in a const variable. Instead, declare it as a regular variable:

var Kilo = math.Pow10(3)

This allows the function call to be executed at runtime.

Alternate Constant Declaration Syntax

For an extensive introduction to Go constants, see the blog post "Constants." Additionally, you can explore the compact syntax for declaring powers of 10 as constants.

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