fix(core): fix build errors in fsharp init-template (#3229)

Author: mikhailshilkov

packages/aws-cdk/lib/init-templates/app/fsharp/src/HelloCdk/HelloCdk.template.fsproj

@@ -15,6 +15,7 @@
     <PackageReference Include="Amazon.CDK" Version="%cdk-version%-devpreview" />
     <PackageReference Include="Amazon.CDK.AWS.IAM" Version="%cdk-version%-devpreview" />
     <PackageReference Include="Amazon.CDK.AWS.SNS" Version="%cdk-version%-devpreview" />
+    <PackageReference Include="Amazon.CDK.AWS.SNS.Subscriptions" Version="%cdk-version%-devpreview" />
     <PackageReference Include="Amazon.CDK.AWS.SQS" Version="%cdk-version%-devpreview" />
   </ItemGroup>
 

packages/aws-cdk/lib/init-templates/app/fsharp/src/HelloCdk/HelloConstruct.fs

@@ -8,13 +8,10 @@ type HelloConstructProps = { BucketCount : int }
 type HelloConstruct(parent, id, props) as this =
     inherit Construct(parent, id)
 
-    let mutable buckets = List.empty
-
-    do
-        buckets <- List.init props.BucketCount
+    let buckets = 
+        List.init props.BucketCount
             (fun i -> Bucket(this, "Bucket" + i.ToString(), BucketProps()))
-        ()
 
     member public __.GrantRead(principal) =
-        List.iter
-            (fun (bucket : Bucket) -> bucket.GrantRead(principal, "*")) buckets
+        buckets
+        |> List.iter (fun bucket -> bucket.GrantRead(principal, "*") |> ignore)

packages/aws-cdk/lib/init-templates/app/fsharp/src/HelloCdk/HelloStack.fs

@@ -2,20 +2,20 @@ namespace HelloCdk
 
 open HelloCdk
 
-open System
 open Amazon.CDK
 open Amazon.CDK.AWS.IAM
 open Amazon.CDK.AWS.SNS
+open Amazon.CDK.AWS.SNS.Subscriptions
 open Amazon.CDK.AWS.SQS
 
 type MyStack(scope, id, props) as this =
     inherit Stack(scope, id, props)
 
-    let queue = Queue(this, "MyFirstQueue", QueueProps(VisibilityTimeout = Duration.Seconds(300)))
+    let queue = Queue(this, "MyFirstQueue", QueueProps(VisibilityTimeout = Duration.Seconds(300.)))
+
     let topic = Topic(this, "MyFirstTopic", TopicProps(DisplayName = "My First Topic Yeah"))
+    do topic.AddSubscription(SqsSubscription(queue, null))
+
     let hello = HelloConstruct(this, "Buckets", { BucketCount = 5 })
     let user = User(this, "MyUser", UserProps())
-
-    do
-        topic.SubscribeQueue(queue, Nullable false) |> ignore
-        hello.GrantRead(user)
+    do hello.GrantRead(user)