[Go] Studying an approach for integration with context.Context

Hi there,

I am new to FoundationDB and was looking around in the issue tracker for closed issues/PRs about this topic but could not find any.

I have been reading also this interesting conversation from 2014: https://groups.google.com/g/golang-nuts/c/SPjQEcsdORA

My question is: how would one integrate Go's `context.Context` when using the Go binding of FoundationDB? I can imagine that the idea has already been explored; ideally I could contribute with some documentation/example/PR afterwards.

I mostly wonder if it would require a re-hash of this old approach for the waiting mechanisms (most likely not): https://gist.github.com/ipeters/4bc867c5e093679ab145
and what guarantees can be kept once `context.Context` is handled.

An example of the use case I am referring to:
```go
package main

import (
"fmt"
"log"
"net/http"

"github.com/apple/foundationdb/bindings/go/src/fdb"
)

var db fdb.Database

func hello(w http.ResponseWriter, req *http.Request) {

// USE-CASE: let's cancel 'db.Transact' when req.Context() is cancelled

ret, e := db.Transact(func(tr fdb.Transaction) (interface{}, error) {
tr.Set(fdb.Key("hello"), []byte("world"))
return tr.Get(fdb.Key("foo")).MustGet(), nil
})
if e != nil {
log.Fatalf("Unable to perform FDB transaction (%v)", e)
}

fmt.Fprintf(w, "hello is now world, foo was: %s\n", string(ret.([]byte)))
}

func main() {
fdb.MustAPIVersion(720)
db = fdb.MustOpenDefault()

http.HandleFunc("/hello", hello)
http.ListenAndServe(":8090", nil)
}

```

Start with the Go binding entry point db.Transact and the request entry point req.Context() shown in the example, then review the linked golang-nuts conversation and waiting-mechanism gist. Done would be a decided, documented approach or scoped implementation plan describing cancellation behavior and its guarantees.

Written by the indexing model from the issue text.