code: func (fs *FlagSet) Int64(names []string, value int64, usage string) *int64 {
  	p := new(int64)
  	fs.Int64Var(p, names, value, usage)
  	return p
  }
docs: // Int64 defines an int64 flag with specified name, default value, and usage string.
  // The return value is the address of an int64 variable that stores the value of the flag.