refactor(xsync): move all sync utilities to xsync

internal/xsync/key_once.go

@@ -0,0 +1,33 @@
+package xsync
+
+import "sync"
+
+// KeyOnce return function that calls make only once per key.
+func KeyOnce[K comparable, V any](do func(K) V) func(K) V {
+	state := keyOnceState[K, V]{
+		onces: map[K]V{},
+		do:    do,
+	}
+	return state.Do
+}
+
+// keyOnceState is map that does call only once per key.
+type keyOnceState[K comparable, V any] struct {
+	onces    map[K]V
+	oncesMux sync.Mutex
+
+	do func(K) V
+}
+
+// Do calls [KeyOnce.Make] once per key and returns value.
+func (k *keyOnceState[K, V]) Do(key K) V {
+	k.oncesMux.Lock()
+	defer k.oncesMux.Unlock()
+
+	val, ok := k.onces[key]
+	if !ok {
+		val = k.do(key)
+		k.onces[key] = val
+	}
+	return val
+}

internal/typedpool/typedpool.go → internal/xsync/pool.go

@@ -1,5 +1,4 @@
-// Package typepool contains generic wrapper around [sync.Pool].
-package typedpool
+package xsync
 
 import "sync"
 

internal/xsync/xsync.go

@@ -0,0 +1,2 @@
+// Package xsync contains synchronization utilities.
+package xsync