add session token support in AWS creds. Closes #329 (#339)

* add session token support in AWS creds. Closes #329

* update README

README.md

@@ -406,7 +406,8 @@ JSON object:
     - `arn` - `string` - required, AWS ARN identifier
     - `region` - `string` - required, region name
     - `awsAccessKeyID` - `string` - optional, AWS API key ID. By default credentials from the [environment](http://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/configuring-sdk.html#specifying-credentials) are used.
-    - `awsSecretAccessKey` - `string` - optional, AWS API key. By default credentials from the [environment](http://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/configuring-sdk.html#specifying-credentials) are used.
+    - `awsSecretAccessKey` - `string` - optional, AWS API access key. By default credentials from the [environment](http://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/configuring-sdk.html#specifying-credentials) are used.
+    - `awsSessionToken` - `string` - optional, AWS session token
   - for HTTP function:
     - `type` - `string` - required, provider type: `http`
     - `url` - `string` - required, the URL of an http or https remote endpoint
@@ -440,6 +441,7 @@ JSON object:
     - `region` - `string` - required, region name
     - `awsAccessKeyID` - `string` - optional, AWS API key ID
     - `awsSecretAccessKey` - `string` - optional, AWS API key
+    - `awsSessionToken` - `string` - optional, AWS session token
   - for HTTP function:
     - `type` - `string` - required, provider type: `http`
     - `url` - `string` - required, the URL of an http or https remote endpoint

functions/function.go

@@ -59,6 +59,7 @@ type Provider struct {
 	Region             string `json:"region,omitempty"`
 	AWSAccessKeyID     string `json:"awsAccessKeyID,omitempty"`
 	AWSSecretAccessKey string `json:"awsSecretAccessKey,omitempty"`
+	AWSSessionToken    string `json:"awsSessionToken,omitempty"`
 
 	// Group weighted function
 	Weighted WeightedFunctions `json:"weighted,omitempty"`
@@ -128,7 +129,7 @@ func (w WeightedFunctions) Choose() (FunctionID, error) {
 func (f *Function) callAWSLambda(payload []byte) ([]byte, error) {
 	config := aws.NewConfig().WithRegion(f.Provider.Region)
 	if f.Provider.AWSAccessKeyID != "" && f.Provider.AWSSecretAccessKey != "" {
-		config = config.WithCredentials(credentials.NewStaticCredentials(f.Provider.AWSAccessKeyID, f.Provider.AWSSecretAccessKey, ""))
+		config = config.WithCredentials(credentials.NewStaticCredentials(f.Provider.AWSAccessKeyID, f.Provider.AWSSecretAccessKey, f.Provider.AWSSessionToken))
 	}
 
 	awslambda := lambda.New(session.New(config))