Adding AWSToken field for temporary credentials (#790)

(cherry picked from commit a5e8773)

README.md

@@ -1292,6 +1292,7 @@ When you initialize an SQS Pump, the SDK uses its default credential chain to fi
 - Environment variables.
   - Static Credentials (`AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, `AWS_SESSION_TOKEN`)
   - Web Identity Token (`AWS_WEB_IDENTITY_TOKEN_FILE`)
+  - Pump Environment Variables (`TYK_PMP_PUMPS_SQS_AWSKEY`, `TYK_PMP_PUMPS_SQS_AWSSECRET`, `TYK_PMP_PUMPS_SQS_AWSTOKEN`)
 - Shared configuration files.
   - SDK defaults to credentials file under `.aws` folder that is placed in the home folder on your computer.
 - If your application uses an ECS task definition or RunTask API operation, IAM role for tasks.
@@ -1311,6 +1312,7 @@ If no credentials are provided, SQS Pump won't be able to connect.
         "aws_region": "us-east-1",
         "aws_key": "key",
         "aws_secret": "secret",
+        "aws_token": "token",
         "aws_endpoint": "http://aws-endpoint:4566",
         "aws_message_group_id": "message_group_id",
         "aws_sqs_batch_limit": 10,

pumps/sqs.go

@@ -56,6 +56,10 @@ type SQSConf struct {
 	// AWSKey is the AWS access key ID used for authentication.
 	AWSKey string `mapstructure:"aws_key"`
 
+	// AWSToken is the AWS session token used for authentication.
+	// This is only required when using temporary credentials.
+	AWSToken string `mapstructure:"aws_token"`
+
 	// AWSEndpoint is the custom endpoint URL for AWS SQS, if applicable.
 	AWSEndpoint string `mapstructure:"aws_endpoint"`
 
@@ -198,7 +202,8 @@ func (s *SQSPump) NewSQSPublisher() (c *sqs.Client, err error) {
 			options.BaseEndpoint = aws.String(s.SQSConf.AWSEndpoint)
 		}
 		if s.SQSConf.AWSKey != "" && s.SQSConf.AWSSecret != "" {
-			options.Credentials = credentials.NewStaticCredentialsProvider(s.SQSConf.AWSKey, s.SQSConf.AWSSecret, "")
+			// Token can be empty since it's optional
+			options.Credentials = credentials.NewStaticCredentialsProvider(s.SQSConf.AWSKey, s.SQSConf.AWSSecret, s.SQSConf.AWSToken)
 		}
 	})