Move version accessor to the opencensus package (#781)

Version returns the OpenCensus library version. It is not an exporter utility.
If it is an exporter utility, it shouldnt be in exportutil. In Go, utility packages
are organized under an existing package.

For example, io/iotuil or net/http/httputil.

Fixes #779.

exporterutil/version.go

@@ -13,8 +13,14 @@
 // limitations under the License.
 
 // Package exporterutil contains common utilities for exporter implementations.
+//
+// Deprecated: Don't use this package.
 package exporterutil
 
+import opencensus "go.opencensus.io"
+
 // Version is the current release version of OpenCensus in use. It is made
 // available for exporters to include in User-Agent-like metadata.
-var Version = "0.13.0"
+var Version = opencensus.Version()
+
+// TODO(jbd): Remove this package at the next release.

internal/check/version.go

@@ -26,7 +26,7 @@ import (
 	"strconv"
 	"strings"
 
-	"go.opencensus.io/exporterutil"
+	opencensus "go.opencensus.io"
 )
 
 func main() {
@@ -48,12 +48,12 @@ func main() {
 		return versionLess(versions[i], versions[j])
 	})
 	latest := versions[len(versions)-1]
-	codeVersion := parseVersion("v" + exporterutil.Version)
+	codeVersion := parseVersion("v" + opencensus.Version())
 	if !versionLess(latest, codeVersion) {
-		fmt.Printf("exporterutil.Version is out of date with Git tags. Got %s; want %s\n", latest, exporterutil.Version)
+		fmt.Printf("exporter.Version is out of date with Git tags. Got %s; want %s\n", latest, opencensus.Version())
 		os.Exit(1)
 	}
-	fmt.Printf("exporterutil.Version is up-to-date: %s\n", exporterutil.Version)
+	fmt.Printf("exporter.Version is up-to-date: %s\n", opencensus.Version())
 }
 
 type version [3]int

internal/internal.go

@@ -18,12 +18,12 @@ import (
 	"fmt"
 	"time"
 
-	"go.opencensus.io/exporterutil"
+	"go.opencensus.io"
 )
 
 // UserAgent is the user agent to be added to the outgoing
 // requests from the exporters.
-var UserAgent = fmt.Sprintf("opencensus-go [%s]", exporterutil.Version)
+var UserAgent = fmt.Sprintf("opencensus-go [%s]", opencensus.Version())
 
 // MonotonicEndTime returns the end time at present
 // but offset from start, monotonically.

doc.go → opencensus.go

@@ -14,3 +14,8 @@
 
 // Package opencensus contains Go support for OpenCensus.
 package opencensus // import "go.opencensus.io"
+
+// Version is the current release version of OpenCensus in use.
+func Version() string {
+	return "0.13.0"
+}