Bumped minimum tested Go version to 1.20.

.github/workflows/main.yml

@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.16.x, 1.x]
+        go-version: [1.20.x, 1.x]
         os: [ubuntu-latest]
         arch: ["", "386"]
       fail-fast: false