title: panic: runtime error: invalid memory address or nil pointer dereference
body: <p>I'm currently working with a Soundcloud wrapper for Go, I want to print the user's followers but it is the first time I face pointer issues.</p>
  
  <p>After building error</p>
  
  <pre><code>panic: runtime error: invalid memory address or nil pointer dereference
  [signal 0xb code=0x1 addr=0x10 pc=0xc9c26]
  </code></pre>
  
  <p>Code</p>
  
  <pre><code>package main
  
  import (
      "fmt"
      "github.com/njasm/gosoundcloud"
  )
  
  
  func main() {
      //  callback url is optional - nil in example
      s, _ := gosoundcloud.NewSoundcloudApi("Client_Id", "Client_Secret", nil)
      var userID uint64 = 1
      member, err := s.GetUser(userID)
      if err != nil {
                 panic(err)
       }
      fmt.Println(member.Followers)
  }
  </code></pre>
  
  <p>After building</p>
  
  <pre><code>goroutine 1 [running]:
  panic(0x3508c0, 0xc82000a0b0)
      /usr/local/go/src/runtime/panic.go:481 +0x3e6
  net/http.(*Client).doFollowingRedirects(0x0, 0xc8200d0000, 0x4611c8, 0x0, 0x0, 0x0)
      /usr/local/go/src/net/http/client.go:429 +0x66
  net/http.(*Client).Do(0x0, 0xc8200d0000, 0x8, 0x0, 0x0)
      /usr/local/go/src/net/http/client.go:188 +0xff
  github.com/njasm/gosoundcloud.(*SoundcloudApi).do(0xc8200c8720, 0xc8200d0000, 0xc820012f00, 0x0, 0x0)
      /Users/ManuelDao/Documents/GoBot/src/github.com/njasm/gosoundcloud/soundcloud.go:217 +0x4b
  github.com/njasm/gosoundcloud.(*SoundcloudApi).Get(0xc8200c8720, 0xc820012f00, 0x22, 0x0, 0x1, 0x0, 0x0)
      /Users/ManuelDao/Documents/GoBot/src/github.com/njasm/gosoundcloud/soundcloud.go:92 +0xe1
  github.com/njasm/gosoundcloud.(*SoundcloudApi).GetUser(0xc8200c8720, 0x1, 0x417a80, 0x0, 0x0)
          /Users/ManuelDao/Documents/GoBot/src/github.com/njasm/gosoundcloud/soundcloud.go:276 +0xc6
  main.main()
          /Users/ManuelDao/Documents/GoBot/src/GoBot/GoBot.go:24 +0x70
  exit status 2
  </code></pre>