Update README.md

Author: horike37

README.md

@@ -125,3 +125,34 @@ stepFunctions:
       role: arn:aws:iam::xxxxxxxx:role/yourRole
       definition:
 ```
+## Tips
+### How to specify the stateMachine ARN to environment variables
+Here is serverless.yml sample to specify the stateMachine ARN to environment variables.
+This makes it possible to trigger your statemachine through Lambda events
+
+```yml
+functions:
+  hello:
+    handler: handler.hello
+  hello:
+    handler: handler.hello2
+    environment:
+        statemachine_arn: ${self:resources.Outputs.HelloStepfunc.Value}
+
+stepFunctions:
+  stateMachines:
+    hellostepfunc:
+      definition:
+        <your definition>
+
+resources:
+  Outputs:
+    HelloStepfunc:
+      Description: The ARN of the example state machine
+      Value:
+        Ref: HellostepfuncStepFunctionsStateMachine
+
+plugins:
+  - serverless-step-functions
+```
+