fixed small typo in oauth2_test.go

Signed-off-by: Matthew Roseman <mroseman95@gmail.com>

oauth2_test.go

@@ -9,7 +9,7 @@ import (
 
 func ExampleApplication() {
 
-	// Authentication Token pulled from environment variable DG_TOKEN
+	// Authentication Token pulled from environment variable DGU_TOKEN
 	Token := os.Getenv("DGU_TOKEN")
 	if Token == "" {
 		return