fix(example): update go.mod, fix task run errors

[fanweixiao]

before:

➜  1-pipeline git:(master) task run
task: [sfn] yomo run -n rand serverless/rand.go
task: [source] cat /dev/urandom | go run source/pipe.go
task: [zipper] yomo serve -c workflow.yaml
[zipper] Using config file: workflow.yaml
[sfn] Using config file: workflow.yaml
[zipper] ℹ️   Running YoMo-Zipper...
[sfn] ℹ️   YoMo Stream Function file: serverless/rand.go
[sfn] ⌛  Create YoMo Stream Function instance...
[zipper] 2022-06-16 11:22:40.372	[yomo:zipper] Listening SIGUSR1, SIGUSR2, SIGTERM/SIGINT...
[zipper] 2022-06-16 11:22:40.373	[core:server] ✅ [example-pipeline][11420] Listening on: [::]:9000, MODE: DEVELOPMENT, QUIC: [v1 draft-29], AUTH: [none]
[sfn] ℹ️   Starting YoMo Stream Function instance with Name: rand. Host: localhost. Port: 9000.
[sfn] ⌛  YoMo Stream Function building...
[source] go: github.com/yomorun/yomo@v1.7.3 requires
[source] 	github.com/emirpasic/gods@v1.18.1: missing go.sum entry; to add it:
[source] 	go mod download github.com/emirpasic/gods
[zipper] 2022-06-16 11:22:40.414	Received signal: interrupt
[zipper] 2022-06-16 11:22:40.414	graceful shutting down ... interrupt
task: Failed to run task "source": exit status 1

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This change is 

[venjiang]

👍