title: Failed to use the AWS greengrasssdk to get thing shadow with error code 404
body: <p>I want to collect some information with my sensor and analyze them  on greengrass core to decide whether send an e-mail by SES to me or not. Everything is ready except my connection between shadow and lambda, which is deployed on my greengrass core. When I try to get information from shadow, I can only get error code like this:</p>
  
  <pre><code>{
    "code": 404,
    "message": "Shadow Not Found",
    "timestamp": 1529392914
  }
  </code></pre>
  
  <p>But actually, the shadow is updated continuously every second. Is there anything that I missed? Or can somebody give me some suggestion? Thanks all!</p>
  
  <pre><code>import greengrasssdk
  
  def lambda_handler(event, context):
  
      seeeduino_client = greengrasssdk.client('iot-data')
      client = greengrasssdk.client('iot-data') # it's used for send data to "Iot Cloud"
  
      response = seeeduino_client.get_thing_shadow(thingName='Seeeduino_Cloud')
      client.publish(
                      topic='load/successed',
                      payload=response["payload"]
                      )
      return
  </code></pre>