testing: update Go versions tested to 1.19-1.21 (#6543)

Author: dfawley

.github/workflows/testing.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Setup Go
         uses: actions/setup-go@v3
         with:
-          go-version: '1.20'
+          go-version: '1.21'
       - name: Checkout repo
         uses: actions/checkout@v3
 
@@ -46,31 +46,31 @@ jobs:
       matrix:
         include:
           - type: vet
-            goversion: '1.20'
+            goversion: '1.21'
 
           - type: tests
-            goversion: '1.20'
+            goversion: '1.21'
 
           - type: tests
-            goversion: '1.20'
+            goversion: '1.21'
             testflags: -race
 
           - type: tests
-            goversion: '1.20'
+            goversion: '1.21'
             goarch: 386
 
           - type: tests
-            goversion: '1.20'
+            goversion: '1.21'
             goarch: arm64
 
           - type: tests
-            goversion: '1.19'
+            goversion: '1.20'
 
           - type: tests
-            goversion: '1.18'
+            goversion: '1.19'
 
           - type: extras
-            goversion: '1.20'
+            goversion: '1.21'
 
     steps:
       # Setup the environment.