test: add exmaple for maputil package

maputil/map.go

@@ -6,7 +6,8 @@ package maputil
 
 import "reflect"
 
-// Keys returns a slice of the map's keys
+// Keys returns a slice of the map's keys.
+// Play: https://go.dev/play/p/xNB5bTb97Wd
 func Keys[K comparable, V any](m map[K]V) []K {
 	keys := make([]K, len(m))
 
@@ -19,7 +20,8 @@ func Keys[K comparable, V any](m map[K]V) []K {
 	return keys
 }
 
-// Values returns a slice of the map's values
+// Values returns a slice of the map's values.
+// Play: https://go.dev/play/p/CBKdUc5FTW6
 func Values[K comparable, V any](m map[K]V) []V {
 	values := make([]V, len(m))
 
@@ -32,7 +34,8 @@ func Values[K comparable, V any](m map[K]V) []V {
 	return values
 }
 
-// Merge maps, next key will overwrite previous key
+// Merge maps, next key will overwrite previous key.
+// Play: https://go.dev/play/p/H95LENF1uB-
 func Merge[K comparable, V any](maps ...map[K]V) map[K]V {
 	result := make(map[K]V, 0)
 
@@ -45,14 +48,16 @@ func Merge[K comparable, V any](maps ...map[K]V) map[K]V {
 	return result
 }
 
-// ForEach executes iteratee funcation for every key and value pair in map
+// ForEach executes iteratee funcation for every key and value pair in map.
+// Play: https://go.dev/play/p/OaThj6iNVXK
 func ForEach[K comparable, V any](m map[K]V, iteratee func(key K, value V)) {
 	for k, v := range m {
 		iteratee(k, v)
 	}
 }
 
-// Filter iterates over map, return a new map contains all key and value pairs pass the predicate function
+// Filter iterates over map, return a new map contains all key and value pairs pass the predicate function.
+// Play: https://go.dev/play/p/fSvF3wxuNG7
 func Filter[K comparable, V any](m map[K]V, predicate func(key K, value V) bool) map[K]V {
 	result := make(map[K]V)
 
@@ -64,7 +69,8 @@ func Filter[K comparable, V any](m map[K]V, predicate func(key K, value V) bool)
 	return result
 }
 
-// Intersect iterates over maps, return a new map of key and value pairs in all given maps
+// Intersect iterates over maps, return a new map of key and value pairs in all given maps.
+// Play: https://go.dev/play/p/Zld0oj3sjcC
 func Intersect[K comparable, V any](maps ...map[K]V) map[K]V {
 	if len(maps) == 0 {
 		return map[K]V{}
@@ -97,7 +103,8 @@ func Intersect[K comparable, V any](maps ...map[K]V) map[K]V {
 	return result
 }
 
-// Minus creates an map of whose key in mapA but not in mapB
+// Minus creates an map of whose key in mapA but not in mapB.
+// Play: https://go.dev/play/p/3u5U9K7YZ9m
 func Minus[K comparable, V any](mapA, mapB map[K]V) map[K]V {
 	result := make(map[K]V)
 
@@ -109,7 +116,8 @@ func Minus[K comparable, V any](mapA, mapB map[K]V) map[K]V {
 	return result
 }
 
-// IsDisjoint two map are disjoint if they have no keys in common
+// IsDisjoint two map are disjoint if they have no keys in common.
+// Play: https://go.dev/play/p/N9qgYg_Ho6f
 func IsDisjoint[K comparable, V any](mapA, mapB map[K]V) bool {
 	for k := range mapA {
 		if _, ok := mapB[k]; ok {