context
package main

import (
	"context"
	"fmt"
)

func f(ctx context.Context) {
	context.WithValue(ctx, "foo", -6)
}

func main() {
	ctx := context.TODO()
	f(ctx)
	fmt.Println(ctx.Value("foo"))
}
  • A. -6
  • B. 0
  • C. <nil>
  • D: panic
Answer
Try it
C
context1
package main

import(
	"fmt"
	"encoding/json"
	"context"
)

func main() {
	data, _ := json.Marshal(context.WithValue(context.Background(), "a", "b"))
	fmt.Println(string(data))
}
Answer
Try it
{"Context":{}}