Add fix for Swift 5.6 (#537)

* Add fix for Swift 5.6

* Update CI to use swift 5.6/5.7

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: macOS-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v1
+      uses: actions/checkout@v3
       with:
         fetch-depth: 1
     - name: SPM tests
@@ -33,7 +33,7 @@ jobs:
           -ignore-filename-regex="\/Tests\/" \
           -instr-profile=.build/debug/codecov/default.profdata > info.lcov
     - name: Upload to codecov.io
-      uses: codecov/codecov-action@v1
+      uses: codecov/codecov-action@v3
       with:
         file: info.lcov
 
@@ -54,15 +54,16 @@ jobs:
     strategy:
       matrix:
         tag:
-          - swift:5.2
           - swift:5.3
           - swift:5.4
           - swift:5.5
+          - swift:5.6
+          - swift:5.7
     container:
       image: ${{ matrix.tag }}
     steps:
     - name: Checkout
-      uses: actions/checkout@v1
+      uses: actions/checkout@v3
       with:
         fetch-depth: 1
     - name: Test
@@ -76,6 +77,6 @@ jobs:
           -ignore-filename-regex="\/Tests\/" \
           -instr-profile .build/debug/codecov/default.profdata > info.lcov
     - name: Upload to codecov.io
-      uses: codecov/codecov-action@v1
+      uses: codecov/codecov-action@v3
       with:
         file: info.lcov

Sources/SotoCore/HTTP/AWSHTTPClient.swift

@@ -53,8 +53,13 @@ public protocol AWSHTTPClient {
     /// Execute an HTTP request with a streamed response
     func execute(request: AWSHTTPRequest, timeout: TimeAmount, on eventLoop: EventLoop, logger: Logger, stream: @escaping ResponseStream) -> EventLoopFuture<AWSHTTPResponse>
 
+#if compiler(>=5.6) && compiler(<5.7)
+    /// This should be called before an HTTP Client can be de-initialised
+    func shutdown(queue: DispatchQueue, _ callback: @escaping @Sendable (Error?) -> Void)
+#else
     /// This should be called before an HTTP Client can be de-initialised
     func shutdown(queue: DispatchQueue, _ callback: @escaping (Error?) -> Void)
+#endif    
 
     /// Event loop group used by client
     var eventLoopGroup: EventLoopGroup { get }