go - How to handle HTTP timeout errors and accessing status codes in golang -

i have code (see below) written in go supposed "fan-out" http requests, , collate/aggregate details back.

i'm new golang , expect me noob , knowledge limited

the output of program like:

{     "status":"success",     "components":[         {"id":"foo","status":200,"body":"..."},         {"id":"bar","status":200,"body":"..."},          {"id":"baz","status":404,"body":"..."},          ...     ] } 

there local server running purposely slow (sleeps 5 seconds , returns response). have other sites listed (see code below) sometime trigger error (if error, that's fine).

the problem have @ moment how best handle these errors, , "timeout" related errors; in i'm not sure how recognise if failure timeout or other error?

at moment blanket error time:

get http://localhost:8080/pugs: read tcp 127.0.0.1:8080: use of closed network connection 

where http://localhost:8080/pugs url failed (hopefully timeout!). can see code (below), i'm not sure how determine error code related timeout nor how access status code of response (i'm blanket setting 404 that's not right - if server error i'd expect 500 status code , i'd reflect in aggregated response send back).

the full code can seen below. appreciated.

    package main      import (             "encoding/json"             "fmt"             "io/ioutil"             "net/http"             "sync"             "time"     )      type component struct {             id  string `json:"id"`             url string `json:"url"`     }      type componentslist struct {             components []component `json:"components"`     }      type componentresponse struct {             id     string             status int             body   string     }      type result struct {             status     string             components []componentresponse     }      var overallstatus string = "success"      func main() {             var cr []componentresponse             var c componentslist              b := []byte(`{"components":[{"id":"local","url":"http://localhost:8080/pugs"},{"id":"google","url":"http://google.com/"},{"id":"integralist","url":"http://integralist.co.uk/"},{"id":"sloooow","url":"http://stevesouders.com/cuzillion/?c0=hj1hfff30_5_f&t=1439194716962"}]}`)              json.unmarshal(b, &c)              var wg sync.waitgroup              timeout := time.duration(1 * time.second)             client := http.client{                     timeout: timeout,             }              i, v := range c.components {                     wg.add(1)                      go func(i int, v component) {                             defer wg.done()                              resp, err := client.get(v.url)                              if err != nil {                                 fmt.printf("problem getting response: %s\n", err)                                  cr = append(cr, componentresponse{                                     v.id,                                     404,                                     err.error(),                                 })                             } else {                                     defer resp.body.close()                                     contents, err := ioutil.readall(resp.body)                                     if err != nil {                                             fmt.printf("problem reading body: %s\n", err)                                     }                                      cr = append(cr, componentresponse{                                             v.id,                                             resp.statuscode,                                             string(contents),                                     })                             }                     }(i, v)             }             wg.wait()              j, err := json.marshal(result{overallstatus, cr})             if err != nil {                     fmt.printf("problem converting json: %s\n", err)                     return             }              fmt.println(string(j))     } 

if want fan out aggregate results , want specific timeout behavior net/http package isn't giving you, may want use goroutines , channels.

i watched video today , walk through scenarios using concurrency features of go. plus, speaker rob pike quite authority -- explains better could.

https://www.youtube.com/watch?v=f6kdp27tyzs