fix(sample): id param is string type

[yiminghe]

PR Type

What kind of change does this PR introduce?

• Fix sample

What is the current behavior?

graphql federation sample does not work when query

{
  post(id: 1) {
    id
    user {
      name
    }
  }
}

What is the new behavior?

graphql federation works

Does this PR introduce a breaking change?

• Yes
• No

[coveralls]

Pull Request Test Coverage Report for Build 8688c944-9aa0-4124-871d-b43a4b378818

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 12 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.006%) to 94.113%

---

Files with Coverage Reduction	New Missed Lines	%
packages/microservices/client/client-kafka.ts	5	95.63%
packages/core/router/router-explorer.ts	7	82.76%

Totals
Change from base Build 2b04a680-b795-4096-8781-3ac877ccaade:	0.006%
Covered Lines:	5771
Relevant Lines:	6132

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💛 - Coveralls