feat: add runners to startup the ocis' services

ocis-pkg/runner/types.go

@@ -0,0 +1,35 @@
+package runner
+
+// Runable represent a task that can be executed by the Runner.
+// It expected to be a long running task with an indefinite execution time,
+// so it's suitable for servers or services.
+// The task can eventually return an error, or nil if the execution finishes
+// without errors
+type Runable func() error
+
+// Stopper represent a function that will stop the Runable.
+// The stopper acts as a notification to the runable to know that the task
+// needs to be finished now.
+//
+// The stopper won't need to crash the runable or force the runable to stop,
+// instead, it will let the runable to know it has to stop and let it finish.
+// This means that the runable might still run for a while.
+//
+// It's recommended the stopper to run asynchronously. This means that the
+// stopper might need to spawn a goroutine. The intention is avoid blocking
+// the running thread.
+//
+// Usually, the stoppers are the servers's `Shutdown()` or `Close()` methods,
+// that will cause the server to start its shutdown procedure. As said, there
+// is no need to force the shutdown, so graceful shutdowns are preferred if
+// they're available
+type Stopper func()
+
+// Result represents the result of a runner.
+// The result contains the provided runner's id (for easier identification
+// in case of multiple results) and the runner's error, which is the result
+// of the Runable function (might be nil if no error happened)
+type Result struct {
+	RunnerID    string
+	RunnerError error
+}