all: mv v1 to next; imp tests, docs

internal/next/agh/agh.go

@@ -0,0 +1,33 @@
+// Package agh contains common entities and interfaces of AdGuard Home.
+//
+// TODO(a.garipov): Move to the upper-level internal/.
+package agh
+
+import "context"
+
+// Service is the interface for API servers.
+//
+// TODO(a.garipov): Consider adding a context to Start.
+//
+// TODO(a.garipov): Consider adding a Wait method or making an extension
+// interface for that.
+type Service interface {
+	// Start starts the service.  It does not block.
+	Start() (err error)
+
+	// Shutdown gracefully stops the service.  ctx is used to determine
+	// a timeout before trying to stop the service less gracefully.
+	Shutdown(ctx context.Context) (err error)
+}
+
+// type check
+var _ Service = EmptyService{}
+
+// EmptyService is a Service that does nothing.
+type EmptyService struct{}
+
+// Start implements the Service interface for EmptyService.
+func (EmptyService) Start() (err error) { return nil }
+
+// Shutdown implements the Service interface for EmptyService.
+func (EmptyService) Shutdown(_ context.Context) (err error) { return nil }