build: update to Go 1.18

lnrpc/routerrpc/router_backend_test.go

@@ -203,7 +203,7 @@ func testQueryRoutes(t *testing.T, useMissionControl bool, useMsat bool,
 			route.Vertex, error) {
 
 			if chanID != 555 {
-				t.Fatal("expected endpoints to be fetched for "+
+				t.Fatalf("expected endpoints to be fetched for "+
 					"channel 555, but got %v instead",
 					chanID)
 			}