runtime: make channels parallelism-safe

src/runtime/scheduler_none.go

@@ -6,6 +6,9 @@ import "internal/task"
 
 const hasScheduler = false
 
+// No goroutines are allowed, so there's no parallelism anywhere.
+const hasParallelism = false
+
 // run is called by the program entry point to execute the go program.
 // With the "none" scheduler, init and the main function are invoked directly.
 func run() {