No restriction on firing goroutines.

### What happened?
On load testing my server with 2000 requests , i generted a pprof trace and turns out over 6,00,000 goroutines were fired during the span. The request endpoint was pretty simple and CPU bound, on firing so many goroutines, they are competing for resource and most of time is getting spend on context switching.
### What did you expect?
There should be a finite version gorountes via worker pool

### Minimal graphql.schema and models to reproduce
an array of type Content {
k: String!
v: String!
}

type ExternalReference {
id: Int!
source: String!
}

### versions
- `go run github.com/99designs/gqlgen version`?
- github.com/99designs/gqlgen v0.17.20
- `go version`? go1.19.3
-

该 issue 提到一个 pprof trace，显示在负载下创建了过多的 goroutine。首先检查 gqlgen codebase 中创建 goroutine 的模式，尤其是 request 处理或 resolver 执行部分。查找现有的并发控制或 worker pool。使用一个简单的 GraphQL schema 重现负载测试，以分析 goroutine 数量。确定应在何处引入 goroutine 限制或 worker pool 机制。

由索引模型根据 Issue 内容生成。