golang strings.Builder type undefined

Question

I was having a problem with the strings.Builder type in GO.

Attempted to run the example code verbatim and GO still responds with:

undefined: strings.Builder

Any clues as to what the problem can be, there's been not other problems at all.

package main

import (
    "fmt"
    "strings"
)

func main() {

    var b strings.Builder
    for i := 3; i >=1; i-- {
        fmt.Fprintf(&b, "%x...", i)
    }
    b.WriteString("ignition")
    fmt.Println(b.String())
}

Answer 1

strings.Builder was added in Go 1.10 (released 2018-02-16, 9 days ago at the time of writing). If you are building using an older version of Go, it won't be available.

Answer 2

If must working with older Go version, you can use bytes.Buffer instead.