Pass the JoindIn speaker id to this program and it will count the amount of talks given at each location

joindin_location_count.go

package main

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

func GetPlace(url string) (string) {
    bodyByteStream := CallUrl(url)

    var bodyInterface interface{}
    json.Unmarshal(bodyByteStream, &bodyInterface)

    bodyMap := bodyInterface.(map[string]interface{})
    eventsMap := bodyMap["events"].([]interface{})
    eventMap := eventsMap[0].(map[string]interface{})
    return eventMap["location"].(string)
}

func CountCitiesForUser(userId int) (map [string] int) {
    bodyByteStream := CallUrl("http://api.joind.in/v2.1/users/" + strconv.Itoa(userId)+"/talks?count=100000&start=0&resultsperpage=100000")
    var bodyInterface interface{}
    json.Unmarshal(bodyByteStream, &bodyInterface)
    bodyMap := bodyInterface.(map[string]interface{})    
    talksMap := bodyMap["talks"].([]interface{})

    var places = make(map[string]int)
    var placeChannel chan string = make(chan string)
    var counter int = 0
    for _, value := range talksMap {
        talkMap := value.(map[string]interface{})
        go func() { 
            placeChannel <- GetPlace(talkMap["event_uri"].(string))            
        } ()                        
        counter++            
    }      
    for i := 0; i < counter; i++ {
        places[<-placeChannel]++
    } 
    return places
}

func CallUrl(url string) ([] byte) {
    resp, err := http.Get(url)
    if err != nil {
        log.Fatal(err)
    }
    defer resp.Body.Close()
    if resp.StatusCode != http.StatusOK {
        log.Fatal(resp.Status)
    }
    bodyByteStream, _ := ioutil.ReadAll(resp.Body)
    return bodyByteStream
}

func main() {
    var user int
    if len(os.Args) == 1 {    
        user = 1975
    } else {
        user,_ = strconv.Atoi(os.Args[1])
    }

    start := time.Now()
    events := CountCitiesForUser(user)
    fmt.Printf("== Amount of talks by JoindIn user %d at location == \n",user)

    for k,v := range events {
        fmt.Printf("Talks given in %s: %d\n",k,v)
    }

    elapsed := time.Since(start)
    fmt.Println("========================")
    fmt.Printf("Elapsed time: %s\n",elapsed)    
}