escape invalid utf8 bytes

main.go

package main

import (
        "fmt"
        "strings"
        "unicode/utf8"
)

func escape(s string) string {
        return strings.Trim(fmt.Sprintf("%q", s), "\"")
}

func check(s string) {
        fmt.Printf("%s is ", s)
        if utf8.ValidString(s) {
                fmt.Println("valid utf8")
        } else {
                fmt.Println("invalid utf8")
        }
}

func main() {
        x := "a\xc5z"

        check(x)
        check(escape(x))
}

result

%go run main.go
a is invalid utf8
a\xc5z is valid utf8