chore: Better error message

lib/mainFn/Daemons.ts

@@ -13,9 +13,10 @@ type Daemon<Ids extends string, Command extends string, Id extends string> = {
     fn: () => Promise<CheckResult> | CheckResult
     trigger?: Trigger
   }
-  requires?: Exclude<Ids, Id>[]
+  requires: Exclude<Ids, Id>[]
 }
 
+type ErrorDuplicateId<Id extends string> = `The id "${Id}" is already used`
 /**
  * Used during the main of a function, it allows us to describe and ensure a set of daemons are running.
  * With the dependency, we are using this like an init system, where we can ensure that a daemon is running
@@ -56,7 +57,12 @@ export class Daemons<Ids extends string> {
     return new Daemons<never>(config.effects, config.started)
   }
   addDaemon<Id extends string, Command extends string>(
-    id: "" extends Id ? never : Id extends Ids ? never : Id,
+    // prettier-ignore
+    id: 
+      "" extends Id ? never :
+      ErrorDuplicateId<Id> extends Id ? never :
+      Id extends Ids ? ErrorDuplicateId<Id> :
+      Id,
     newDaemon: Omit<Daemon<Ids, Command, Id>, "id">,
   ) {
     const daemons = ((this?.daemons ?? []) as any[]).concat({
@@ -98,7 +104,6 @@ export class Daemons<Ids extends string> {
           }
           resolve(child)
         })
-        return child
       })
     }
     return {