Go web API for TLD checking

tlds.go

package main

import (
    "fmt"
    "net/http"
    "os"
    "time"
    "io/ioutil"
    "encoding/json"
    "strings"
)

func check(tldsChannel chan []string) []string {
  url := "https://data.iana.org/TLD/tlds-alpha-by-domain.txt"

  res, err := http.Get(url)
  perror(err)

  body, err := ioutil.ReadAll(res.Body)
  perror(err)

  tlds := strings.Split(string(body), "\n")
  tlds = tlds[1:len(tlds)-1]

  tldsChannel <- lowercaseSlice(tlds)

  return tlds
}

func checker(tldsChannel chan []string) {
  for {
      select {
          case <-time.After(6 * time.Hour):
              check(tldsChannel)
      }
  }
}

func manager(tldsChannel chan []string) {
  curr_stuff := check(tldsChannel)

  go checker(tldsChannel)

  for {
      select {
          case new_stuff := <-tldsChannel:
              curr_stuff = new_stuff
              tldsChannel <- curr_stuff
          default:
              tldsChannel <- curr_stuff
        }
    }
}

func main() {
    tldsChannel := make(chan []string)

    go manager(tldsChannel)

    http.HandleFunc("/all", func(res http.ResponseWriter, req *http.Request) {
        jsonResponse, err := json.Marshal(<-tldsChannel)
        perror(err)
        fmt.Fprintln(res, string(jsonResponse))
    })

    http.HandleFunc("/check", func(res http.ResponseWriter, req *http.Request) {
        q := req.URL.Query()
        v := q.Get("tld")

        if (stringInSlice(v,<-tldsChannel)) {
            fmt.Fprintln(res, "true")
        } else {
            fmt.Fprintln(res, "false")
        }
    })

    err := http.ListenAndServe(":"+os.Getenv("PORT"), nil)
    perror(err)
}

func stringInSlice(s string, slice []string) bool {
    for _, item := range slice {
        if item == s {
            return true
        }
    }
    return false
}

func lowercaseSlice(slice []string) []string {
    for index := range slice {
        slice[index] = strings.ToLower(slice[index])
    }
    return slice
}

func perror(err error) {
    if err != nil {
        panic(err)
    }
}

API endpoints:

• http://tlds.herokuapp.com/all returns a JSON array of all valid TLDs
• http://tlds.herokuapp.com/check?tld=org returns true if org is a valid TLD, and false otherwise