chore: use go1.18.3 (#816)

This diff changes all github actions and mk to use go1.18.3.

That's what I am using locally.

Also, both oohttp and oocrypto are on go1.18.3 already.

.github/workflows/jafar.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v1
         with:
-          go-version: "1.18.2"
+          go-version: "1.18.3"
       - uses: actions/checkout@v2
       - run: go build -v ./internal/cmd/jafar
       - run: sudo ./testjafar.bash