go version devel +1a9d124153b9 Sat Jul 05 08:48:46 2014 +0400 windows/386

If I run the following:
package main

import (
        "os"
        "strings"
)

func main() {
    longf := strings.Repeat("f", 240)
    
    _, e1 := os.Lstat("/tmp/" + longf)
    if e1 != nil {
        println(e1.Error())
    }
}

The result is [string too long]

If you shrink the repeat down eventually you will get
GetFileAttributesEx
/tmp/ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff:
The system cannot find the file specified.