For I/O you can buffer inside the application whether the respective file is readable/writeable or not. If it's not readable you can directly switch to another

For I/O you can buffer inside the application whether the respective file is readable/writeable or not. If it's not readable you can directly switch to another goroutine without invoking a syscall. The scheduler will later get notified by select/epoll that the file is readable/writeable, adjust the buffered status and reschedule the goroutine. But ok, for reading you might often have a buffered state of readable while in reality it's not and you only get this information through EAGAIN on read, so you won't avoid the syscall there. For writing you most likely always would.