Add context.Context support

[gwvandesteeg]

Add support on transactions and queries to use the standard context.Context objects to determine timeouts, deadlines, and cancellations for a request.

For example, expanding the Session type with a

RunWithContext(ctx context.Context, cyper string, params map[string]interface{}, configurers ...func(*TransactinConfig)) (Result, error)

When building a microservice such as a REST API that needs to do a Cypher query, being able to pass in the received requests context to the query to handle cancellations and graceful shutdowns properly is really a must have to avoid leaving goroutines deadlocked in the background.

A sample use would be

import (
        "http"
	n4jdriver "github.com/neo4j/neo4j-go-driver/neo4j"
)

type Neo4JConnection struct {
  Driver n4jdriver.Driver
}

func (conn Neo4JConnection) GetUser(w http.ResponseWriter, r *http.Request) {
        var result n4jdriver.Result

        guid, ok  := r.URL.Query()["guid"]
        if !ok {
                // handle the lack of guid
        }
	session, err := conn.Driver.Session(n4jdriver.AccessModeWrite)
	if err != nil {
		// handle the error
	}
	defer session.Close()

        dataset := map[string]interface{}{
            guid: guid,
        } 

        result, err := session.RunWithContext(r.Context(), `
MATCH (u:User {guid: $guid}) RETURN u.guid, u.fullname
`, dataset)
    if err != nil {
        // handle the error, which could be a context timeout or deadline exceeded or a cancellation
    }
    // do something with the data and return it to the end user

}

[2hdddg]

@gwvandesteeg this is a good suggestion. The 1.7 driver is currently reworked to be pure Go (v1.8) which would make the implementation of context better (context can go a lot deeper into the internals).

I'm not sure if we want to add an API for providing context on 1.8 driver but the underlying implementations will more or less use contexts. I'm putting this into the list of requested features for the 4.0 driver (version scheme now follows server versions).

[damianopetrungaro]

@2hdddg do you need help on this?
I need to make context management around all the session to make sure it won't block longer than the context deadline.

[arjantop-cai]

@2hdddg Any plans for this? As I see it did not make it in the 4.x version

[lukestoward]

Hi @2hdddg, i'm guessing there still is no support for context?

[fbiville]

Hello, current Go driver maintainer here (Peter moved to Kernel a year ago).
There are now context-aware APIs in the 5.0 branch. It's about to be released in preview mode this week.

[fbiville]

Hey everyone, the experimental, pre-release 5.0.0-preview is out and includes these context-aware APIs.
You can give it a... go 🥁: https://github.com/neo4j/neo4j-go-driver/releases/tag/v5.0.0-preview