title: Login to bigquery from golang using json keyfile
body: <p>So I have a json keyfile that looks like this:</p>
  
  <pre><code>{
    "user_agent": null,
    "_scopes": "https://www.googleapis.com/auth/bigquery",
    "token_uri": "https://www.googleapis.com/oauth2/v4/token",
    "refresh_token": null,
    "_service_account_email": "...",
    "assertion_type": null,
    "_kwargs": {},
    "revoke_uri": "https://accounts.google.com/o/oauth2/revoke",
    "_private_key_pkcs8_pem": "-----BEGIN PRIVATE KEY----- ..."
    ...
  }
  </code></pre>
  
  <p>I want to login using this file to bigquery, with Golang. I looked through the examples at <a href="https://github.com/GoogleCloudPlatform/google-cloud-go" rel="noreferrer">https://github.com/GoogleCloudPlatform/google-cloud-go</a> but couldn't find anything related there how to create a new bigquery client using the keyfile. Am I missing something obvious?</p>
  
  <p>In python the quivalent is:</p>
  
  <pre><code>        credentials = ServiceAccountCredentials.from_json_keyfile_name(
                  'keyfile.json',
                  'https://www.googleapis.com/auth/bigquery')
  
          ...
  </code></pre>