What is the correct way to find the min between two integers in Go?

Until Go 1.18 a one-off function was the standard way; for example, the stdlib's sort.go does it near the top of the file:

func min(a, b int) int {
    if a < b {
        return a
    }
    return b
}

You might still want or need to use this approach so your code works on Go versions below 1.18!

Starting with Go 1.18, you can write a generic min function which is just as efficient at run time as the hand-coded single-type version, but works with any type with < and > operators:

func min[T constraints.Ordered](a, b T) T {
    if a < b {
        return a
    }
    return b
}

func main() {
    fmt.Println(min(1, 2))
    fmt.Println(min(1.5, 2.5))
    fmt.Println(min("Hello", "世界"))
}

There's been discussion of updating the stdlib to add generic versions of existing functions, but if that happens it won't be until a later version.

math.Min(2, 3) happened to work because numeric constants in Go are untyped. Beware of treating float64s as a universal number type in general, though, since integers above 2^53 will get rounded if converted to float64.

There is no built-in min or max function for integers, but it’s simple to write your own. Thanks to support for variadic functions we can even compare more integers with just one call:

func MinOf(vars ...int) int {
    min := vars[0]

    for _, i := range vars {
        if min > i {
            min = i
        }
    }

    return min
}

Usage:

MinOf(3, 9, 6, 2)

Similarly here is the max function:

func MaxOf(vars ...int) int {
    max := vars[0]

    for _, i := range vars {
        if max < i {
            max = i
        }
    }

    return max
}