chore: update doc of FindKey

Author: WingGao

presence.go

@@ -56,7 +56,7 @@ func Find(arr interface{}, predicate interface{}) interface{} {
 }
 
 // Find iterates over elements of collection, returning the first
-// element predicate returns truthy for.
+// element of an array and random of a map which predicate returns truthy for.
 func FindKey(arr interface{}, predicate interface{}) (matchKey, matchEle interface{}) {
 	if !IsIteratee(arr) {
 		panic("First parameter must be an iteratee")

presence_test.go

@@ -154,7 +154,7 @@ func TestFindKey(t *testing.T) {
 	is := assert.New(t)
 
 	k, r := FindKey(map[string]int{"a": 1, "b": 2, "c": 3, "d": 4}, func(x int) bool {
-		return x%2 == 0
+		return x == 2
 	})
 
 	is.Equal(r, 2)