package main

import (
    "fmt"
    "regexp"
)

func main() {
    s1 := "FooBar"
    s2 := "Foo/Bar"
    s3 := "foobar/"
    s4 := ""
    
    r := regexp.MustCompile("^[A-Za-z0-9_]+$")
    fmt.Println(r.MatchString(s1))
    fmt.Println(r.MatchString(s2))
    fmt.Println(r.MatchString(s3))
    fmt.Println(r.MatchString(s4))
}