Code cleanup and missing error checks

internal/auth/callback.go

@@ -17,6 +17,7 @@ package auth
 
 import (
 	"fmt"
+	"log"
 	"net/http"
 	"net/url"
 
@@ -34,5 +35,12 @@ func RunOauth2CallbackServer(redirectURL url.URL, param string, responseChan cha
 		}
 	})
 
-	go http.ListenAndServe(redirectURL.Host, nil)
+	go runServer(redirectURL.Host)
+}
+
+func runServer(addr string) {
+	err := http.ListenAndServe(addr, nil)
+	if err != nil {
+		log.Fatal(err)
+	}
 }