title: Golang flag: Ignore missing flag and parse multiple duplicate flags
body: <p>I am new to Golang and I have been unable to find a solution to this problem using flag.</p>
  
  <p>How can I use flag so my program can handle calls like these, where the -term flag may be present a variable number of times, including 0 times:</p>
  
  <pre><code>./myprogram -f flag1
  ./myprogram -f flag1 -term t1 -term t2 -term  t3
  </code></pre>