title: How to authenticate with service account and bigrquery package?
body: <p>I have been able to authenticate using the json file associated with a service account using <code>googleAuth</code> and <code>bigQueryR</code>.</p>
  
  <pre><code># Load Packages
  global.packages &lt;- c("bigQueryR", "googleAuthR")
  
  ### Apply require on the list of packages; load them quietly
  lapply(global.packages, require, character.only = TRUE, quietly = TRUE)
  
  Sys.setenv("GCS_AUTH_FILE" = "json_file_location")
  
  #Authenticate Google BQ
  googleAuthR::gar_attach_auto_auth("https://www.googleapis.com/auth/bigquery",
                                    environment_var = "GCS_AUTH_FILE")
  </code></pre>
  
  <p>This works and I am able to start using functions from <code>bigQueryR</code>.</p>
  
  <p>Now assume I am limited to the <code>bigrquery</code> package, how can I authenticate using a service account with this package? </p>
  
  <p>I have looked at the documentation here to no avail:
  <a href="https://cran.r-project.org/web/packages/bigrquery/bigrquery.pdf" rel="noreferrer">https://cran.r-project.org/web/packages/bigrquery/bigrquery.pdf</a></p>
  
  <p>The resources I have come across on the internet propose using the 
  <code>bigQueryR</code> package in place of <code>bigrquery</code>. </p>
  
  <p>For instance this related stackoverflow question:
  <a href="https://stackoverflow.com/questions/26263003/use-bigrquery-auth-in-shiny-application">Use bigrquery auth in shiny application</a>.</p>
  
  <p>But I need functions only available in <code>bigrquery</code>.</p>