Update hashcode.go

Updating the comment `we need and non negative integer` to `we need a non negative integer`

helper/hashcode/hashcode.go

@@ -9,7 +9,7 @@ import (
 // String hashes a string to a unique hashcode.
 //
 // crc32 returns a uint32, but for our use we need
-// and non negative integer. Here we cast to an integer
+// a non negative integer. Here we cast to an integer
 // and invert it if the result is negative.
 func String(s string) int {
 	v := int(crc32.ChecksumIEEE([]byte(s)))