title: ruby&postgres Ruby connects to database error in macOS environment
body: <p>this is my database.rb</p>
  <pre><code>#!/usr/bin/ruby
  require 'postgres'
  
  conn = PGconn.connect(&quot;localhost&quot;, 5432, '', '', &quot;postgres&quot;, &quot;postgres&quot;, &quot;postgre&quot;)
  
  res  = conn.exec('select tablename, tableowner from pg_tables')
  
  res.each do |row|
      row.each do |column|
          print column
          (20-column.length).times{print &quot; &quot;}
      end
      puts
  end
  </code></pre>
  <p>executable file:
  <em>ruby database.rb</em></p>
  <pre><code>Traceback (most recent call last):
    11: from database.rb:4:in `&lt;main&gt;'
    10: from database.rb:4:in `new'
     9: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/postgres-compat.rb:28:in `initialize'
     8: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/postgres-compat.rb:28:in `new'
     7: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/connection.rb:58:in `initialize'
     6: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/connection.rb:58:in `loop'
     5: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/connection.rb:59:in `block in initialize'
     4: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/message.rb:58:in `read'
     3: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/message.rb:116:in `create'
     2: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/message.rb:137:in `parse'
     1: from /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/message.rb:82:in `parse'
  /Library/Ruby/Gems/2.6.0/gems/postgres-pr-0.7.0/lib/postgres-pr/message.rb:139:in `block in parse': undefined method `auth_type' for #&lt;PostgresPR::UnknownAuthType:0x0000000133830f98&gt; (NoMethodError)
  </code></pre>
  <p><strong>What should i do next？</strong></p>