func hashByMultiplicationMethod(key string, tableSize int) int32 {
   keyChars := []rune(key)
   var keyChar int32
   constantA := 0.618
   for i := 0; i < len(keyChars); i++ {
       // try to make hashcode become different
       keyChar = keyChar + keyChars[i] + keyChar%11
   }
   hashResult := float64(tableSize) * math.Mod(float64(keyChar)*constantA, 1)
   return int32(math.Floor(hashResult))
}