Golang example of context in API Clients

client.go

package api

import (
  "encoding/json"

  "golang.org/x/net/context"
  "golang.org/x/net/context/ctxhttp"
)

type Client {
}

type Response {
  id string
}

func NewClient() *Client {
  client := &Client{}
  
  return client
}

func (c *Client) FetchResource(ctx context.Context, endpoint string) (*Response, error) {
  res, err := ctxhttp.Get("http://api.example.com/v1/" + endpoint)
  
  if err != nil {
    return nil, err
  }
  
  defer res.Body.Close()
  
  decoder := json.NewDecoder(res.Body)
  var data Response
  err = decoder.Decode(&data)
  
  if err != nil {
    return nil, err
  }
  
  return &data, nil
}

main.go

package main

import (
  "log"
  "time"
  
  "example/api"
	"golang.org/x/net/context"
)

func fetch(ctx context.Context, client *api.Client, endpoint string) (*api.Response, error) {
  ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
  defer cancel()
  return client.FetchResource(endpoint)
}

func main() {
  client := api.NewClient()
  
  ctx := context.Background()
  resp, err := fetch(ctx, client, "foobar")
  
  if err != nil {
    log.Fatal(err)  // 2016/05/02 15:30:00 context deadline exceeded
                    // exit status 1
  }
  
  fmt.Println("foobar response: %s", resp.id)
}