ci: update for go1.20
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 001b5e4..b94f980 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,7 +12,7 @@
       matrix:
         # Do not move this line; it is referred to by README.md.
         # Versions of Go that are explicitly supported by Gonum.
-        go-version: [1.19.x, 1.18.x]
+        go-version: [1.20.x, 1.19.x]
         platform: [ubuntu-latest, macos-latest]
         force-goarch: ["", "386"]
         tags: 
diff --git a/.github/workflows/codecov.yml b/.github/workflows/codecov.yml
index 0b66a23..dc49bb6 100644
--- a/.github/workflows/codecov.yml
+++ b/.github/workflows/codecov.yml
@@ -13,7 +13,7 @@
     if: github.event.pull_request.merged == true
     strategy:
       matrix:
-        go-version: [1.19.x]
+        go-version: [1.20.x]
         platform: [ubuntu-latest]
         tags: 
           - ""