envflag.go
func IntVar(p *int, name string, value int, usage string) {
	EnvironmentFlags.IntVar(p, name, value, usage)
}
func IntVar(p *int, name string, value int, usage string) {
	EnvironmentFlags.IntVar(p, name, value, usage)
}
// IntVar defines an int flag with specified name, default value, and
// usage string.  The argument p points to an int variable in which to
// store the value of the flag.