Use default pool, make adapter context optional

packages/net/src/Pool.ts

@@ -19,10 +19,20 @@ export type PoolOptions = {
   makeSocket?: (url: string) => Socket
 }
 
+export let poolSingleton: Pool
+
 export class Pool {
   _data = new Map<string, Socket>()
   _subs: PoolSubscription[] = []
 
+  static getSingleton() {
+    if (!poolSingleton) {
+      poolSingleton = new Pool()
+    }
+
+    return poolSingleton
+  }
+
   constructor(readonly options: PoolOptions = {}) {}
 
   has(url: string) {