Helper Context

Passing context into a helper lets the helper read request-scoped data.

helper_context.go

package main

import (
	"context"
	"fmt"
)

type requestKey string

func labelRequest(ctx context.Context, action string) string {
	id := ctx.Value(requestKey("id"))
	return fmt.Sprintf("%v:%s", id, action)
}

func main() {
	var action = 
	ctx := context.WithValue(context.Background(), requestKey("id"), "req-7")

	label := labelRequest(ctx, action)
	fmt.Println("action=", action)
	fmt.Println("label=", label)
}

package main

import (
	"context"
	"fmt"
)

type requestKey string

func labelRequest(ctx context.Context, action string) string {
	id := ctx.Value(requestKey("id"))
	return fmt.Sprintf("%v:%s", id, action)
}

func main() {
	var action = 
	ctx := context.WithValue(context.Background(), requestKey("id"), "req-7")

	label := labelRequest(ctx, action)
	fmt.Println("action=", action)
	fmt.Println("label=", label)
}

package main

import (
	"context"
	"fmt"
)

type requestKey string

func labelRequest(ctx context.Context, action string) string {
	id := ctx.Value(requestKey("id"))
	return fmt.Sprintf("%v:%s", id, action)
}

func main() {
	var action = 
	ctx := context.WithValue(context.Background(), requestKey("id"), "req-7")

	label := labelRequest(ctx, action)
	fmt.Println("action=", action)
	fmt.Println("label=", label)
}

pass context Functions usually accept a context as their first parameter so callers can pass values and cancellation.