Should cancelling a context interrupt an ongoing operation?

[wayan]

I try to interrupt ongoing SNMP GET operation (on unreachable Target). I pass a Context to GoSNMP struct and then cancel the context, but the cancel is ignored and the operation continues until timeout - code below takes approx 25 seconds to finish instead of 2 seconds.

Is this behaviour a feature? If so, how can I interrupt ongoing operation (in case of shutdown for example)? By closing the snmp connection?

package main

import (
    "context"
    "fmt"
    "log"
    "time"

    g "github.com/gosnmp/gosnmp"
)

func main() {

    ctx, cancel := context.WithCancel(context.Background())
    go func() {
        time.Sleep(2 * time.Second)
        fmt.Println("Cancelling")
        cancel()
    }()

    g.Default.Target = "192.168.1.10"
    g.Default.Timeout = 25 * time.Second
    g.Default.Retries = 0
    g.Default.Context = ctx

    err := g.Default.Connect()
    if err != nil {
        log.Fatalf("Connect() err: %v", err)
    }
    defer g.Default.Conn.Close()

    _, err = g.Default.Get([]string{"1.3.6.1.2.1.1.4.0"})
    if err != nil {
        log.Fatalf("Get() err: %v", err)
    }

}