Maint: healthcheck package interface rework

- return concrete struct type
- Add compilation checks for implementations

internal/healthcheck/run.go

@@ -0,0 +1,40 @@
+package healthcheck
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"time"
+)
+
+func (s *Server) Run(ctx context.Context, done chan<- struct{}) {
+	defer close(done)
+
+	loopDone := make(chan struct{})
+	go s.runHealthcheckLoop(ctx, loopDone)
+
+	server := http.Server{
+		Addr:    s.config.ServerAddress,
+		Handler: s.handler,
+	}
+	serverDone := make(chan struct{})
+	go func() {
+		defer close(serverDone)
+		<-ctx.Done()
+		const shutdownGraceDuration = 2 * time.Second
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), shutdownGraceDuration)
+		defer cancel()
+		if err := server.Shutdown(shutdownCtx); err != nil {
+			s.logger.Error("failed shutting down: " + err.Error())
+		}
+	}()
+
+	s.logger.Info("listening on " + s.config.ServerAddress)
+	err := server.ListenAndServe()
+	if err != nil && !errors.Is(ctx.Err(), context.Canceled) {
+		s.logger.Error(err.Error())
+	}
+
+	<-loopDone
+	<-serverDone
+}