feat: add healthcheck (#141)

* feat: add healtcheck app

Signed-off-by: rare-magma <rare-magma@posteo.eu>

* feat: add healthz endpoint

Signed-off-by: rare-magma <rare-magma@posteo.eu>

* ci: add healthcheck directive to dockerfile

Signed-off-by: rare-magma <rare-magma@posteo.eu>

---------

Signed-off-by: rare-magma <rare-magma@posteo.eu>

src/healthcheck/healthcheck.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		log.Fatal("Expected URL as command-line argument")
+		os.Exit(1)
+	}
+	url := os.Args[1]
+	fmt.Println(url)
+	if _, err := http.Get(url); err != nil {
+		os.Exit(1)
+	}
+}