remove unnecessary preconcurrency imports (#28)

* remove unnecessary preconcurrency imports

motivation: eliminate warnings

changes: require swift 5.7 and remove unnecessary preconcurrency imports for foundation

* fixup

Author: tomerd

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.6
+// swift-tools-version:5.7
 
 import PackageDescription
 

Sources/AWSLambdaEvents/Cloudwatch.swift

@@ -12,10 +12,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=5.6)
-@preconcurrency import struct Foundation.Date
-#else
+#if canImport(Darwin)
 import struct Foundation.Date
+#else
+@preconcurrency import struct Foundation.Date
 #endif
 
 /// EventBridge has the same events/notification types as CloudWatch

Sources/AWSLambdaEvents/DynamoDB.swift

@@ -12,10 +12,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=5.6)
-@preconcurrency import struct Foundation.Date
-#else
+#if canImport(Darwin)
 import struct Foundation.Date
+#else
+@preconcurrency import struct Foundation.Date
 #endif
 
 // https://docs.aws.amazon.com/lambda/latest/dg/with-ddb.html

Sources/AWSLambdaEvents/Utils/DateWrappers.swift

@@ -12,10 +12,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-#if swift(>=5.6)
-@preconcurrency import struct Foundation.Date
-#else
+#if canImport(Darwin)
 import struct Foundation.Date
+#else
+@preconcurrency import struct Foundation.Date
 #endif
 import class Foundation.DateFormatter
 import struct Foundation.Locale

docker/docker-compose.al2.54.yaml

@@ -6,7 +6,7 @@ services:
     image: swift-aws-lambda-events:al2-5.7
     build:
       args:
-        base_image: "swiftlang/swift:nightly-main-amazonlinux2"
+        swift_version: "5.7"
 
   test:
     image: swift-aws-lambda-events:al2-5.7

docker/docker-compose.al2.55.yaml

@@ -1,6 +1,6 @@
 # this file is not designed to be run directly
 # instead, use the docker-compose.<os>.<swift> files
-# eg docker-compose -f docker/docker-compose.yaml -f docker/docker-compose.al2.52.yaml run test
+# eg docker-compose -f docker/docker-compose.yaml -f docker/docker-compose.al2.57.yaml run test
 version: "3"
 
 services: