Make sure that event loop of task is the same as event loop of channel

Sources/AsyncHTTPClient/HTTPClient.swift

@@ -123,7 +123,7 @@ public class HTTPClient {
 
         let task = Task<T.Response>(eventLoop: eventLoop)
 
-        var bootstrap = ClientBootstrap(group: self.eventLoopGroup)
+        var bootstrap = ClientBootstrap(group: eventLoop)
             .channelOption(ChannelOptions.socket(SocketOptionLevel(IPPROTO_TCP), TCP_NODELAY), value: 1)
             .channelInitializer { channel in
                 let encoder = HTTPRequestEncoder()

Sources/AsyncHTTPClient/HTTPHandler.swift

@@ -271,6 +271,7 @@ extension HTTPClient {
         }
 
         func setChannel(_ channel: Channel) -> Channel {
+            precondition(self.eventLoop === channel.eventLoop, "Channel must use same event loop as this task.")
             return self.lock.withLock {
                 self.channel = channel
                 return channel

Tests/AsyncHTTPClientTests/HTTPClientTests+XCTest.swift

@@ -27,6 +27,7 @@ extension HTTPClientTests {
         return [
             ("testRequestURI", testRequestURI),
             ("testGet", testGet),
+            ("testGetWithSharedEventLoopGroup", testGetWithSharedEventLoopGroup),
             ("testPost", testPost),
             ("testGetHttps", testGetHttps),
             ("testPostHttps", testPostHttps),

Tests/AsyncHTTPClientTests/HTTPClientTests.swift

@@ -44,6 +44,25 @@ class HTTPClientTests: XCTestCase {
         let response = try httpClient.get(url: "http://localhost:\(httpBin.port)/get").wait()
         XCTAssertEqual(.ok, response.status)
     }
+
+    func testGetWithSharedEventLoopGroup() throws {
+        let httpBin = HttpBin()
+        let elg = MultiThreadedEventLoopGroup(numberOfThreads: 8)
+        let httpClient = HTTPClient(eventLoopGroupProvider: .shared(elg))
+        defer {
+            try! elg.syncShutdownGracefully()
+            httpBin.shutdown()
+        }
+
+        let delegate = TestHTTPDelegate()
+        let request = try HTTPClient.Request(url: "http://localhost:\(httpBin.port)/events/10/1")
+        let task = httpClient.execute(request: request, delegate: delegate)
+        let expectedEventLoop = task.eventLoop
+        task.futureResult.whenComplete { (_) in
+            XCTAssertTrue(expectedEventLoop.inEventLoop)
+        }
+        try task.wait()
+    }
 
     func testPost() throws {
         let httpBin = HttpBin()