golang-ci: Upgrade, skipping the white space complainer

.golangci.yml

@@ -14,9 +14,10 @@ linters:
     - scopelint
     - gocyclo
     - funlen
+    - wsl
 
 service:
-  golangci-lint-version: 1.19.x
+  golangci-lint-version: 1.21.x
   prepare:
     - rm -f go.sum # 1.12 -> 1.13 issues with QUIC-go
     - GO111MODULE=on go mod vendor