Merge pull request #98 from orcaman/calc_key_length_once

Calc key length once

Author: orcaman

concurrent_map.go

@@ -312,7 +312,8 @@ func (m ConcurrentMap) MarshalJSON() ([]byte, error) {
 func fnv32(key string) uint32 {
 	hash := uint32(2166136261)
 	const prime32 = uint32(16777619)
-	for i := 0; i < len(key); i++ {
+	keyLength := len(key)
+	for i := 0; i < keyLength; i++ {
 		hash *= prime32
 		hash ^= uint32(key[i])
 	}