move session creation out of SSMStore constructor for reuse

store/shared.go

@@ -0,0 +1,40 @@
+package store
+
+import (
+	"os"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/ec2metadata"
+	"github.com/aws/aws-sdk-go/aws/session"
+)
+
+const (
+	RegionEnvVar = "CHAMBER_AWS_REGION"
+)
+
+func getSession(numRetries int) (*session.Session, *string) {
+	var region *string
+
+	if regionOverride, ok := os.LookupEnv(RegionEnvVar); ok {
+		region = aws.String(regionOverride)
+	}
+	retSession := session.Must(session.NewSessionWithOptions(
+		session.Options{
+			Config: aws.Config{
+				Region: region,
+			},
+			SharedConfigState: session.SharedConfigEnable,
+		},
+	))
+
+	// If region is still not set, attempt to determine it via ec2 metadata API
+	if aws.StringValue(retSession.Config.Region) == "" {
+		session := session.New()
+		ec2metadataSvc := ec2metadata.New(session)
+		if regionOverride, err := ec2metadataSvc.Region(); err == nil {
+			region = aws.String(regionOverride)
+		}
+	}
+
+	return retSession, region
+}

store/ssmstore.go

@@ -9,8 +9,6 @@ import (
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
-	"github.com/aws/aws-sdk-go/aws/ec2metadata"
-	"github.com/aws/aws-sdk-go/aws/session"
 	"github.com/aws/aws-sdk-go/service/ssm"
 	"github.com/aws/aws-sdk-go/service/ssm/ssmiface"
 )
@@ -40,29 +38,8 @@ type SSMStore struct {
 
 // NewSSMStore creates a new SSMStore
 func NewSSMStore(numRetries int) *SSMStore {
-	var region *string
+	ssmSession, region := getSession(numRetries)
 
-	if regionOverride, ok := os.LookupEnv("CHAMBER_AWS_REGION"); ok {
-		region = aws.String(regionOverride)
-	}
-	ssmSession := session.Must(session.NewSessionWithOptions(
-		session.Options{
-			Config: aws.Config{
-				Region: region,
-			},
-			SharedConfigState: session.SharedConfigEnable,
-		},
-	))
-
-	// If region is still not set, attempt to determine it via ec2 metadata API
-	region = nil
-	if aws.StringValue(ssmSession.Config.Region) == "" {
-		session := session.New()
-		ec2metadataSvc := ec2metadata.New(session)
-		if regionOverride, err := ec2metadataSvc.Region(); err == nil {
-			region = aws.String(regionOverride)
-		}
-	}
 	svc := ssm.New(ssmSession, &aws.Config{
 		MaxRetries: aws.Int(numRetries),
 		Region:     region,