chore: support latest four Go versions (#51)

.github/workflows/tests.yaml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: [1.15, 1.16, 1.17]
+        go-version: [1.14, 1.15, 1.16, 1.17]
     steps:
       - name: Setup Go ${{ matrix.go-version }}
         uses: actions/setup-go@v2

README.md

@@ -123,11 +123,11 @@ myDialer, err := cloudsqlconn.NewDialer(
 
 ### Enabling Metrics and Tracing
 
-This library includes support for metrics and tracing using [OpenCensus][]. 
-To enable metrics or tracing, you need to configure an [exporter][]. 
-OpenCensus supports many backends for exporters. 
+This library includes support for metrics and tracing using [OpenCensus][].
+To enable metrics or tracing, you need to configure an [exporter][].
+OpenCensus supports many backends for exporters.
 
-For example, to use [Cloud Monitoring][] and [Cloud Trace][], you would 
+For example, to use [Cloud Monitoring][] and [Cloud Trace][], you would
 configure an exporter like so:
 
 ``` golang
@@ -142,7 +142,7 @@ func main() {
     sd, err := stackdriver.NewExporter(stackdriver.Options{
         ProjectID: "mycoolproject",
     })
-    if err != nil {    
+    if err != nil {
         // handle error
     }
     defer sd.Flush()
@@ -156,6 +156,11 @@ func main() {
 }
 ```
 
+## Go Versions Supported
+
+We support the latest four Go versions. Changes in supported Go versions will be
+considered a minor and not a major change.
+
 [OpenCensus]: https://opencensus.io/introduction/
 [exporter]: https://opencensus.io/exporters/
 [Cloud Trace]: https://cloud.google.com/trace