add staticcheck linting (#3828)

cleanup to add linter

    grpc change:
        https://godoc.org/google.golang.org/grpc#WithContextDialer
        https://godoc.org/google.golang.org/grpc#WithDialer
        grpc/grpc-go#2627
    prometheous change:
        due to UninstrumentedHandler, being deprecated in the future
    empty branch = empty if or else statement
        didn't delete them entirely but commented
        couldn't find a reason to have them
    could not replicate the issue #3406
        but if want to keep it commented then we should comment out the if statement as well

rpc/lib/client/ws_client_test.go

@@ -212,7 +212,8 @@ func callWgDoneOnResult(t *testing.T, c *WSClient, wg *sync.WaitGroup) {
 		select {
 		case resp := <-c.ResponsesCh:
 			if resp.Error != nil {
-				t.Fatalf("unexpected error: %v", resp.Error)
+				t.Errorf("unexpected error: %v", resp.Error)
+				return
 			}
 			if resp.Result != nil {
 				wg.Done()