Add structured coroutines and explicit error handling

examples/http_server.gt

@@ -36,18 +36,6 @@ class EpicControllerImpl(val db: *bun.DB) {
     }
 }
 
-worker Counter {
-    var counter = 0
-
-    fun getCount(): Int {
-        return counter
-    }
-    fun increment() {
-        counter += 1
-        println(counter)
-    }
-}
-
 fun main() {
     val postgresDsn = "postgresql://postgres:postgres@localhost/postgres?sslmode=disable"
     val sqlDb = sql.OpenDB(
@@ -56,21 +44,10 @@ fun main() {
         )
     )
     val db = bun.NewDB(sqlDb, pgdialect.New())
-    val counter = Counter()
-    go {
-        while(true) {
-        select {
-            every(1000) -> counter.increment()
-        }
-    }
-    }
     val epicController = EpicControllerImpl(db)
     fmt.Println("serving http://localhost:8080")
     http.HandleFunc("/", epicController.hello)
     http.HandleFunc("/bun", epicController.bunHealth)
     http.HandleFunc("/bun/users", epicController.bunUsers)
-    http.HandleFunc("/counter") { w, r ->
-        fmt.Fprintln(w, "bun users total:", counter.getCount())
-    }
     http.ListenAndServe(":8080", http.DefaultServeMux)
 }

examples/mapping.gt

@@ -16,13 +16,13 @@ enum ResponseState {
 
 data class AccountEntity(
     var id: String,
-    var address: *AddressEntity,
+    var address: AddressEntity,
     var labels: List<String>,
     var state: EntityState
 )
 
 data class AccountResponse(
-    var address: *AddressResponse,
+    var address: AddressResponse,
     var id: String,
     var labels: List<String>,
     var state: ResponseState

examples/nullability.gt

@@ -0,0 +1,18 @@
+package main
+
+data class User(var email: String)
+
+fun emailOrMissing(user: User?): String {
+    if (user == null) { return "missing" }
+    return user.email
+}
+
+fun optionalEmail(user: User?): String? {
+    return user?.email
+}
+
+fun main() {
+    val user: User? = User("user@example.com")
+    println(emailOrMissing(user))
+    println(user!!.email)
+}

examples/results.gt

@@ -0,0 +1,18 @@
+package main
+
+import strconv
+import os
+
+fun parse(value: String): Result<Int, Error> {
+    return strconv.atoi(value)
+}
+
+fun changeDirectory(path: String): Result<Unit, Error> {
+    return os.chdir(path)
+}
+
+fun main() {
+    println(parse("42").unwrap())
+    println(parse("invalid").unwrapOr(0))
+    changeDirectory(".").unwrap()
+}

examples/showcase.gt

@@ -13,25 +13,6 @@ class PrefixGreeter(val prefix: String): Greeter {
     }
 }
 
-worker Counter {
-    var count = 0
-
-    fun increment() {
-        count += 1
-    }
-
-    fun value(): Int {
-        return count
-    }
-}
-
-fun risky(input: String): String {
-    if (input == "boom") {
-        throw "boom requested"
-    }
-    return input
-}
-
 fun main() {
     val greeter: Greeter = PrefixGreeter("hello")
     println(greeter.greet("gotlin"))
@@ -44,35 +25,25 @@ fun main() {
     val upper = strings.ToUpper("gotlin")
     fmt.Println("interop:", upper)
 
-    val result = runCatching({ risky("boom") })
-    if (result.isSuccess()) {
-        println("runCatching: success")
-    } else {
-        println("runCatching:")
-        println(result.exceptionOrNull())
-    }
-
-    val maybe: any = null
+    val maybe: String? = null
     if (maybe == null) {
         println("null check works")
     }
 
-    val counter = Counter()
-    counter.increment()
-    counter.increment()
-    fmt.Println("worker value:", counter.value())
-
-    val ready = Channel<String>()
-    go {
-        select {
-            after(120) -> ready.send("timer fired")
+    runBlocking {
+        val ready = Channel<String>()
+        launch {
+            delay(120)
+            ready.send("timer fired")
+        }
+        select {
+            ready -> println("channel says: " + it)
         }
-    }
-    select {
-        ready -> println("channel says: " + it)
-    }
 
-    select {
-        every(50) -> println("one periodic tick")
+        val answer = async<Int> {
+            delay(50)
+            return 42
+        }
+        fmt.Println("async value:", answer.await())
     }
 }