fix race in backpressure tests (#46)

* fix race in backpressure tests

Author: artemredkin

Tests/NIOHTTPClientTests/SwiftNIOHTTPTests.swift

@@ -14,6 +14,7 @@
 
 import Foundation
 import NIO
+import NIOConcurrencyHelpers
 import NIOFoundationCompat
 @testable import NIOHTTP1
 @testable import NIOHTTPClient
@@ -405,15 +406,25 @@ class SwiftHTTPTests: XCTestCase {
  class BackpressureTestDelegate: HTTPClientResponseDelegate {
  typealias Response = Void
 
- var reads = 0
+ var _reads = 0
+ let lock: Lock
  let promise: EventLoopPromise<Void>
 
  init(promise: EventLoopPromise<Void>) {
+ self.lock = Lock()
  self.promise = promise
  }
 
+ var reads: Int {
+ return self.lock.withLock {
+ self._reads
+ }
+ }
+
  func didReceivePart(task: HTTPClient.Task<Response>, _ buffer: ByteBuffer) -> EventLoopFuture<Void> {
- self.reads += 1
+ self.lock.withLockVoid {
+ self._reads += 1
+ }
  return self.promise.futureResult
  }