Fix go 1.18 compatibility (#138)

Author: echistyakov

internal/socket/subscriber_request_response.go

@@ -3,14 +3,14 @@ package socket
 import (
 	"context"
 	"sync"
-	"sync/atomic"
 
 	"github.com/jjeffcaii/reactor-go"
 	"github.com/rsocket/rsocket-go/core"
 	"github.com/rsocket/rsocket-go/internal/common"
 	"github.com/rsocket/rsocket-go/internal/fragmentation"
 	"github.com/rsocket/rsocket-go/payload"
 	"github.com/rsocket/rsocket-go/rx"
+	"go.uber.org/atomic"
 )
 
 var globalRequestResponseSubscriberPool requestResponseSubscriberPool