code: func GBToByte(n interface{}) int64 {
  	switch v := n.(type) {
  	case int:
  		return int64(v * 1000000000)
  	case int32:
  		return int64(v * 1000000000)
  	case int64:
  		return v * 1000000000
  	}
  	panic(fmt.Errorf("non-integer type %T for value", n))
  }
docs: // GBToByte returns n*1000000000.
  //
  // The output is returned as int64 - if another type is needed, it needs to be
  // cast. Remember that int32 overflows at 2GB and uint32 will overflow at 4GB.