如何在OS X El Capitan上安装ngrok?

首先，我尝试从ngrok-stable-darwin-amd64.zip网站下载.当我尝试通过终端解压缩时，我得到:

First I tried downloading from the website, ngrok-stable-darwin-amd64.zip. When I try unzipping via Terminal, I get:

Archive:  /Users/User/Downloads/ngrok-stable-darwin-amd64.zip
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of /Users/User/Downloads/ngrok-stable-darwin-amd64.zip or
        /Users/User/Downloads/ngrok-stable-darwin-amd64.zip.zip, and cannot find /Users/User/Downloads/ngrok-stable-darwin-amd64.zip.ZIP, period.

使用Unarchiver解压缩的响应如下:

Unzipping with Unarchiver responds with:

读取文件内容时出现问题 "ngrok-stable-darwin-amd64.zip":数据已损坏

There was a problem while reading the contents of the file "ngrok-stable-darwin-amd64.zip": Data is corrupted

尝试了自酿路线brew cask install ngrok，但无济于事:

Tried the homebrew route, brew cask install ngrok, to no avail:

==> Downloading https://bin.equinox.io/c/4VmDzA7iaHb/ngrok-stable-darwin-amd64.z
#####                                                                      7.0%
curl: (56) SSLRead() return error -9806
Error: Download failed on Cask 'ngrok' with message: Download failed: https://bin.equinox.io/c/4VmDzA7iaHb/ngrok-stable-darwin-amd64.zip
The incomplete download is cached at /Users/User/Library/Caches/Homebrew/Cask/ngrok--2.1.3,4VmDzA7iaHb.zip.incomplete

我正在尝试启用 Vagant share .为什么我不能安装ngrok，或更重要的是，我该怎么办?

I'm trying to enable Vagrant share. Why can't I install ngrok, or more importantly, how can I?

请&谢谢.