drop support for Go 1.20, build on Go 1.22rc1 on CI (#4195)

* drop support for Go 1.20

* ci: udpate CircleCI to Go 1.21

* qtls: remove unnecessary type aliases

* ci: build using Go 1.22rc1

.github/workflows/integration.yml

@@ -6,7 +6,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu" ]
-        go: [ "1.20.x", "1.21.x" ]
+        go: [ "1.21.x", "1.22.0-rc.1" ]
         include:
           - os: "windows"
             go: "1.21.x"
@@ -22,7 +22,7 @@ jobs:
     name: Integration Tests (${{ matrix.os }}, Go ${{ matrix.go }})
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-go@v4
+      - uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go }}
       - run: go version