title: Best way to use HTTP client in a concurrent application
body: <p>First I'll describe my case.
  I have to do HTTPS requests to several APIs from my application and they should be ran concurrently.
  I want to know if I should use a separate HTTP client per goroutine or I can share one client across all goroutines. Of course I'd like to enjoy connection reusing/pooling offered by the HTTP client, but I am concerned about it being thread(aka goroutine)-safe and if the client will run requests concurrently or they'll in fact be sequenced?</p>