run init in a goroutine

src/runtime/runtime_wasm.go

@@ -22,6 +22,10 @@ func postinit() {}
 
 //export _start
 func _start() {
+	// These need to be initialized early so that the heap can be initialized.
+	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd = uintptr(wasm_memory_size(0) * wasmPageSize)
+
 	run()
 }