Why can't I declare a constant map in Golang?

Error: Golang's Restriction on Constant Maps

In Golang, attempting to declare a constant map like the following will result in an error:

const (
    running = map[string]string{
        "one": "ONE",
        "two": "TWO",
    }
)

Reason for Restriction

The error stems from the fact that Golang restricts constant values to specific types. According to the language specification, only the following can be declared as constants:

• Rune
• Integer
• Floating-point
• Imaginary
• String
• Identifiers denoting a constant
• Constant expressions
• Result values of built-in functions (e.g., unsafe.Sizeof, cap, len, real, imag, complex)

Nature of Maps

Arrays, slices, and maps are not included in this list of allowed types for constants. While maps appear to be similar to arrays and slices since they have an indexed structure, they are not considered numeric types and therefore cannot be declared as constants.

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